Buy the AMPLock LPC-VR. Among these four, it is the one whose manufacturer publishes a warranty term, states the conditions attached to it, and is honest about what the product cannot do. It also brings a disc cylinder and ten pounds of ductile and stainless steel.
If lube-plate clearance is your main concern, shortlist the Proven PL-5: the maker explicitly lists space for one. Confirm the actual plate and pin-box combination before buying. The TRIMAX TFW60 offers a full collar and push-button locking; the Blaylock TL-70 uses an aluminum collar. We do not have published weights for both to support a lightest-lock ranking.
Quick picks
Best overall
AMPLock LPC-VR
The only lock here whose maker publishes both a warranty term and its conditions — plus a disc cylinder and two weight options.
Best for lube-plate clearance
Proven PL-5
A welded steel collar with clearance for a lube plate, and the only one offering a cylinder upgrade path.
Best mass-market
TRIMAX TFW60
Full collar, push-button locking and keyed-alike compatibility with other TRIMAX products.
Aluminum option
Blaylock TL-70
An aluminum collar secured by a hardened steel pin; confirm fit, weight and padlock requirements before ordering.
How the four compare
| Model | Material | Cylinder | Origin | Warranty | Price | Buy |
|---|---|---|---|---|---|---|
| AMPLock LPC-VR | Ductile steel and stainless steel, with all moving parts stainless | Anti-picking disc lock with a rotating face intended to prevent drilling | Canada | 5 years, registration required within 30 days | $$$$ | Check price(opens in a new tab) |
| Proven PL-5 | — | Cobra 7-pin tubular as standard. Proven disc detainer is a paid upgrade; Medeco M3 and Abloy available on request | Majority manufactured in the USA, per Proven Industries | Not published on the product page | $$$$ | Check price(opens in a new tab) |
| TRIMAX TFW60 | Alloy, described by TRIMAX as rugged and ultra-tough | Push-button locking mechanism; cylinder grade not specified | Not specified by the manufacturer | Not stated on the product page, which links to a warranty form | $$$ | Check price(opens in a new tab) |
| Blaylock TL-70 | Blaylock's page states "hand forged in the USA using the highest quality aircraft grade aluminum" while also describing the collar as cast — the two descriptions are not reconciled on the page | — | USA, per Blaylock | Not published on the product page | $$ | Check price(opens in a new tab) |
What a king pin lock is actually protecting against
A king pin lock is intended to obstruct normal hitch coupling while the fifth wheel is unhitched. Its effectiveness depends on fit, construction and the attack; we have no evidence here for a universal theft time or success rate.
Treat it as one layer alongside your storage arrangements. AMPLock’s warranty explicitly says its protection is limited and does not insure against theft. Published warranty terms help assess after-sales cover, but do not prove attack resistance.
The documentation gap is the story here
We check every product against the manufacturer’s own pages rather than retailer listings, and this category produced the thinnest set we have encountered.
| Published on the maker’s own product page | AMPLock | Proven | TRIMAX | Blaylock |
|---|---|---|---|---|
| Warranty term | Yes — 5 years | No | No | No |
| Warranty conditions | Yes | No | No | No |
| Cylinder type | Yes | Yes | Partly | No |
| Material | Yes | Yes | Partly | Contradictory |
| Weight | Yes | No | No | No |
| Which king pins it fits | No | Yes | No | Partly |
The three other product pages reviewed here do not state a warranty term. Retailers fill the gap with numbers — 90 days for the Blaylock, limited lifetime for the TRIMAX — but those are not confirmable at source, so they are not published as specifications here.
What actually decides fitment
Start with the actual pin specification. A nominal 2-inch kingpin is a common fitment — for example, CURT specifies that size for its kingpin lock — but a matching diameter does not establish that a lock fits the complete assembly.
Compare the lock’s whole shape with the space around your kingpin. These are conceptual side sections, not dimensions or a fit guarantee for any model.
1. Check the pin and lock
Confirm the specified pin diameter and profile. Then check whether the body can reach its locking position and whether you can operate the key or securing pin.
2. Check what surrounds it
Check lube-plate thickness and any wedge, capture plate or other nearby hardware fitted to your exact setup. Do not remove required hitch parts just to make a lock fit.
Before ordering: identify the pin box and accessories → send the lock maker the model, photos and requested measurements → confirm the exact lock variant. Trailer weight is not a lock-clearance measurement.
Examples: Proven PL-5 lists lube-plate clearance; AMPLock lists a separate Pullrite/Sidewinder-style model. Neither statement establishes compatibility with every accessory combination. A lube plate works at the hitch-plate interface; follow the hitch maker’s remaining lubrication instructions.
Lube plate. It adds material below the pin-box plate. Proven publishes lube-plate clearance for the PL-5, but no numeric allowance on the product page. Confirm your actual plate thickness. Do not treat a lube plate as a substitute for every lubrication step specified by the hitch maker.
Pin-box hardware. A Sidewinder wedge and a PullRite SuperGlide capture plate are examples of hardware to identify. These are different hitch arrangements. AMPLock’s separately listed Pullrite/Sidewinder-style model is a reason to check the exact assembly with the manufacturer, not proof that every rotating pin box needs the same lock.
Lock body and access. Check the full envelope, its approach to the pin and space to operate the key or securing pin. The lock must seat and latch as its instructions require. Trailer weight is not a clearance specification.
The locks
Best overall
AMPLock LPC-VR Fifth Wheel King Pin Lock
Why it's here
What separates AMPLock from the rest of this category is not the steel, it is the paperwork. It is the only company here that publishes a warranty length, spells out the registration requirement, names its exclusions, and states plainly that its product is not insurance. Every one of those disclosures makes the offer look worse on paper than a competitor claiming a lifetime warranty and defining nothing, which is exactly why it is worth something.
The lock itself is a moulded ductile iron and stainless body with a disc cylinder and a rotating anti-drill face — the same design language as AMPLock’s coupler locks, and the same argument for a close fit that leaves no gap to work a tool into.
Full specifications
| Lock Type | King pin lock |
|---|---|
| Fits | Fifth wheel king pins on commercial rigs, RVs and travel trailers. AMPLock does not publish the king pin sizes or pin box types on the product page |
| Cylinder Type | Anti-picking disc lock with a rotating face intended to prevent drilling |
| Material | Ductile steel and stainless steel, with all moving parts stainless |
| Weight (lb) | 10 (Ultimate) or 5 (Strong), depending on version |
| Dimensions | 7 x 6 x 8.26 in (Ultimate); 5.11 x 4 x 4 in (Strong) |
| Attack Resistance | AMPLock claims resistance to cutting, prying, oxy-fuel cutting, saws and drills — a manufacturer claim, not an independent result |
| Corrosion Resistance | Stated suitable for all climates |
| Country Of Origin | Canada |
| Warranty | 5 years, registration required within 30 days |
Specifications verified August 13, 2026 from Pullrite/Sidewinder-style variant and fitment qualification reviewed 2026-11-06 , AMPLock LPC-VR product page — materials, cylinder, weights, dimensions, origin , AMPLock warranty page — 5-year term, 30-day registration requirement, exclusions .
Strengths
- The only maker here publishing a warranty term and its conditions on its own pages
- Anti-picking disc cylinder with a rotating face intended to defeat drilling
- Ductile and stainless steel with all moving parts stainless — the right choice for something living outdoors
- Sold in two weights, so 10 lb on the pin is a choice rather than a requirement
- A separately listed Pullrite/Sidewinder-style model; ask AMPLock which fits your assembly
Weaknesses
- The 5-year term requires registration within 30 days of purchase — miss that window and you have no cover
- Warranty covers manufacturing defects only, and excludes anything bought from an unauthorised reseller
- AMPLock does not publish which king pin sizes or pin box types the standard model fits
- The cutting, prying and oxy-fuel resistance claims are the manufacturer's own, with no independent testing behind them
Fit: AMPLock lists a separate Pullrite/Sidewinder-style model. Confirm the actual pin-box model, lube plate, wedge or capture plate and clearances with the maker before choosing a variant. A rotating pin box alone does not identify the correct lock for every accessory combination.
Buy it if
You want the lock whose maker is most willing to put its terms in writing, and you will register it the week it arrives.
Choose something else if
Your exact pin box and fitted accessories have not been confirmed compatible.
Best for lube-plate clearance
Proven Industries Model PL-5 5th Wheel King Pin Lock
Why it's here
The published lube-plate clearance is a useful starting point. It does not replace confirmation of your plate thickness and nearby hardware, and the reference to heavy rigs is not evidence of a better fit on a heavier trailer.
The cylinder caveat is the same one that applies to Proven’s coupler locks, and seeing it twice makes it a brand policy worth knowing rather than a quirk of one product. The standard Cobra cylinder is tubular and the disc detainer is an upgrade. Confirm the exact option in the listing; cylinder type alone does not establish a security rating or a measured defeat time.
Full specifications
| Lock Type | King pin lock |
|---|---|
| Fits | Marketed for all fifth-wheel kingpins; confirm the actual pin box and accessories |
| Collar | Solid steel welded collar, with clearance to accommodate a lube plate |
| Pin | 303 stainless steel |
| Pin Diameter | Not specified by the manufacturer |
| Cylinder Type | Cobra 7-pin tubular as standard. Proven disc detainer is a paid upgrade; Medeco M3 and Abloy available on request |
| Keyed Alike | Can be keyed to Proven's entire lock line |
| Weight (lb) | Not specified by the manufacturer |
| Country Of Origin | Majority manufactured in the USA, per Proven Industries |
| Warranty | Not published on the product page |
Specifications verified August 13, 2026 from PL-5 lube-plate clearance and fitment scope rechecked 2026-11-06 , Proven Industries Model PL-5 product page — construction, cylinder options, lube plate clearance, pricing .
Strengths
- Solid steel welded collar marketed for fifth wheels and commercial trailers; not a towing load rating
- Explicit clearance for a lube plate — the one fitment detail most makers ignore
- 303 stainless steel securing pin
- The only lock here with a cylinder upgrade path, up to Medeco M3 and Abloy
- Can be keyed to Proven's entire lock line, so a coupler lock and a king pin lock share one key
Weaknesses
- Ships with a 7-pin tubular cylinder as standard — the disc detainer is a paid upgrade, same as on Proven's coupler locks
- No warranty published on the product page at all
- No published weight, and no published pin diameter
- Among the most expensive options before you add the better cylinder
Fit: Proven lists additional lube-plate clearance but no numeric thickness allowance. Confirm your plate and nearby hardware with the manufacturer. The reference to heavy trailers is not a lock-clearance or towing-load rating.
Buy it if
You need confirmed lube-plate clearance or already own Proven locks and want matching keys.
Choose something else if
You are buying the base configuration expecting a high-security cylinder. Budget for the upgrade or look at the AMPLock.
Best mass-market
TRIMAX TFW60 5th Wheel King Pin Lock
Why it's here
The push-button action deserves more credit than it usually gets. A king pin lock that is awkward to fit is a lock that stays in the storage bay, and the combination of a full collar and one-handed locking is why this is the model most fifth wheel owners actually end up with.
The trade-off is that TRIMAX publishes almost nothing. No fitment list, no weight, no origin, no warranty term on the page — just a link to a warranty form. It is very likely fine. You are simply taking that on trust.
Full specifications
| Lock Type | King pin lock |
|---|---|
| Fits | Not specified by the manufacturer — TRIMAX describes it only as suiting unattended trailers |
| Collar | Full collar design, which also keeps grease off your hands |
| Material | Alloy, described by TRIMAX as rugged and ultra-tough |
| Cylinder Type | Push-button locking mechanism; cylinder grade not specified |
| Finish | Weatherproof epoxy powder coat against rust and corrosion |
| Keys Included | 2 |
| Keyed Alike | Can be keyed alike to other TRIMAX products |
| Weight (lb) | Not specified by the manufacturer |
| Country Of Origin | Not specified by the manufacturer |
| Warranty | Not stated on the product page, which links to a warranty form |
Specifications verified August 13, 2026 from TRIMAX TFW60 product page — construction, locking action, finish, keying, price .
Strengths
- Full collar design that encloses the pin and keeps grease off your hands
- Push-button locking, which is the difference between a lock you use and one you skip
- Weatherproof epoxy powder coat — the right finish for something stored outdoors
- Keyed alike to other TRIMAX products, including their receiver and coupler locks
Weaknesses
- TRIMAX does not publish which king pins it fits, its weight, its country of manufacture, or a warranty term
- The cylinder grade behind the push button is not specified anywhere
- "Rugged, ultra-tough alloy" is a description, not a material specification
- The retail claim of a limited lifetime warranty covers rust and corrosion — a materials warranty, not cover against the lock being defeated
Fit: The full collar is the practical selling point — a king pin carries grease, and a lock that encloses it is a lock you will actually fit rather than avoid. TRIMAX does not publish which king pins it fits, so confirm before ordering if your pin box is unusual.
Buy it if
You want a visible, easy-to-use lock at a sensible price and you are already buying into the TRIMAX keyed-alike system.
Choose something else if
You want to know what you are buying. This is the least documented lock here after the Blaylock.
Aluminum option
Blaylock EZ Lock TL-70 King Pin Coupler Lock
Why it's here
Blaylock has been making these for a long time and the design is proven in the ordinary sense of the word. But this is the least documented product on the page: the manufacturer publishes no pin diameter, no weight, no warranty term, and no answer to the fairly basic question of whether a padlock comes in the box.
The forged-versus-cast contradiction on their own product page is a small thing, and we would not raise it if the page carried the other numbers. On a page that carries almost none, it is the difference between a specification and a description.
Full specifications
| Lock Type | King pin lock |
|---|---|
| Fits | 18-wheelers and the heaviest 5th wheel RVs, per Blaylock |
| Collar | Cast aluminium collar held in place with a hardened steel pin |
| Material | Blaylock's page states "hand forged in the USA using the highest quality aircraft grade aluminum" while also describing the collar as cast — the two descriptions are not reconciled on the page |
| Pin Diameter | Not specified by the manufacturer |
| Weight (lb) | Not specified by the manufacturer |
| Padlock Included | Not stated by the manufacturer |
| Country Of Origin | USA, per Blaylock |
| Warranty | Not published on the product page |
Specifications verified August 13, 2026 from Published fitment information and absence of weight rechecked 2026-11-06 , Blaylock King Pin Coupler Lock TL-70 product page — construction, fitment claim, origin .
Strengths
- Aluminum collar; no manufacturer weight figure available for comparison
- Blaylock markets it for fifth wheels and commercial trailers; confirm actual fit
- Hardened steel pin securing the collar
- Made in the USA, per Blaylock
Weaknesses
- Blaylock's own page describes the lock as both hand forged and cast — different processes with different strengths, unreconciled
- No published warranty term, pin diameter, weight, or statement of whether a padlock is included
- Retail listings state a 90-day warranty, which would be by far the shortest here — but that is not confirmable at Blaylock
- Aluminum is more workable than steel for anyone attacking it with tools
Fit: An aluminum-collar option, but no manufacturer weight figure supports a lightest-lock ranking. Confirm pin fit, surrounding clearance and padlock requirements; the product page does not specify these measurements.
Buy it if
You want deterrence on a budget and you are content to buy on the brand's reputation rather than on published figures.
Choose something else if
You want a warranty you can read, or you are protecting a high-value rig in open storage.
How to choose
Start with the complete pin-box assembly. Record the pin specification, lube plate and any surrounding hardware. Confirm the exact lock variant and that it can fully close without changing required hitch parts.
Read the warranty as a signal, not just as cover. A company willing to publish “5 years, register within 30 days, defects only, not an insurer” is telling you it has thought about the failure cases. A company publishing nothing may be equally good — but you have no way to know, and that is the point.
Check the cylinder separately from the body. Ten pounds of steel around a weak cylinder is a heavy lock, not a secure one. Only AMPLock and Proven name their cylinder types, and Proven’s best one costs extra.
Buy the one you will actually fit. A king pin is greasy and sits at an awkward height. A full collar and a one-handed action are the reason a lock gets used every time rather than on the trips you remember.
Consider keying it alike. Both Proven and TRIMAX will key a king pin lock to their other products. If you already run a coupler or receiver lock from either, one key across the set removes the most common reason locks go unused.
What we left out, and why
The marketplace roundups’ picks. Most pages ranking for this search are generalist affiliate sites — several of them recommending locks whose specs are quoted in millimeters from marketplace listings. Where a manufacturer publishes nothing verifiable, there is nothing for us to compare.
TRIMAX TFW80HD. The hardened steel version of the TFW60 rather than the alloy one, and probably the better buy of the two. Retail listings describe it in detail; we could not confirm those specifications on TRIMAX’s own pages, so it is noted here rather than reviewed.
Wheel and boot locks. A different layer of security for the same rig, protecting against a different attack, and a separate purchase decision.
Bumper-pull coupler locks. If your trailer connects by a ball rather than a king pin, this is the wrong page — see the best trailer hitch locks instead, and what size coupler lock you need for the fitment question.
Questions worth answering
Do king pin locks actually stop fifth wheel theft?
A correctly fitted lock obstructs normal coupling to an unhitched fifth wheel. It is one security layer, not a guarantee against theft. AMPLock's warranty expressly limits its protection and does not insure the trailer.
What size king pin do fifth wheels use?
A 2-inch kingpin is a common RV fitment, but confirm the actual pin specification against the lock maker's requirements. Matching that size is only the first check: lube plates and nearby pin-box hardware can prevent a lock body from seating and closing.
Will a king pin lock fit over a lube plate?
Check the exact lock and lube-plate combination. Proven lists extra clearance for a lube plate on the PL-5, but does not give a universal thickness allowance. A lube plate replaces grease at the hitch-plate interface where the hitch maker permits it; it does not cancel other lubrication requirements.
What is a sidewinder pin box and does it need a different lock?
A Sidewinder relocates the turning pivot; a PullRite hitch is a different system and may use a capture plate. These details can change lock clearance. AMPLock lists a separate Pullrite/Sidewinder-style lock, but confirm the exact pin box and fitted accessories with the lock maker.
Should I lock the king pin or the coupler?
A fifth wheel uses a kingpin at the truck connection; a bumper-pull trailer uses a ball coupler. A storage lock must match that connection. Neither type is a complete theft-prevention system on its own.
Are the cheap king pin locks worth buying?
A visible lock on the pin does deterrent work even if it is not formidable, so a budget lock beats none. What you give up is documentation: the cheaper the lock in this category, the less its maker publishes about pin diameter, weight, cylinder grade or warranty. Buy one knowing you are buying on the brand's word.