Buy the AMPLock LPC-VR. It is the only lock in this category 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 your rig is heavy or runs a lube plate, the Proven PL-5 is the better mechanical fit — a welded steel collar with clearance designed in, and the only lock here you can order with a better cylinder than the one it ships with. For most owners the TRIMAX TFW60 does the job at a third of the price, and the Blaylock TL-70 is the lightest and cheapest thing you can put on a pin.
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 10 lb of steel.
Best for heavy rigs
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 across a whole lock line, at a third of the premium price.
Lightest
Blaylock TL-70
Aluminum rather than steel, and the cheapest way to put something visible on the pin — with the least published about it.
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 stored fifth wheel is the easiest large theft in the RV world. The king pin is a standardised steel shaft, any truck with a fifth wheel hitch in the bed can couple to it, and the whole operation takes under a minute and looks exactly like an owner collecting their own RV. Nobody in a storage yard looks twice.
That is the threat model, and it explains why this category is shaped the way it is. The lock does not need to survive a workshop. It needs to make coupling impossible without tools, and to be visible enough from a distance that the rig stops being the easy one in the row.
It also explains the honest limit. AMPLock puts it in its own warranty document: the company “is not an insurer, and the protection provided by its products is limited and not absolute in case of theft”. That is the most candid sentence published by anyone in this category, and it is worth more than the security adjectives on the rest of the pages you will read.
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 |
Three of four manufacturers publish no warranty term at all. 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
Not the pin. Fifth wheel king pins are standardised, which is why nearly every lock here advertises fitting everything from travel trailers to 18-wheelers. What varies is the space around the pin.
Lube plate. If you run a plastic or composite lube plate instead of greasing the pin, there is extra material for the lock to clear. Proven states explicitly that the PL-5 accommodates one. Most makers say nothing either way, which is not the same as saying yes.
Sidewinder and rotating pin boxes. These move the pivot point to buy turning clearance with a short-bed truck, and they change the geometry enough that AMPLock sells a separate lock for Pullrite and sidewinder-style boxes. If that is your setup, the standard model is the wrong order.
Collar style. A full collar encloses the pin, which keeps grease off your hands and gives a would-be thief less to grip. A partial bracket is lighter and cheaper. TRIMAX and Proven both use full collars; the Blaylock is a bracket with a pin through it.
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 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 dedicated model for Pullrite and sidewinder pin boxes, which almost nobody else addresses
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 sells a separate king pin lock for Pullrite and Sidewinder-style pin boxes. If your fifth wheel uses a rotating or sidewinder pin box, confirm which model applies before ordering — the standard lock is not the one you want.
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
You run a sidewinder pin box and order the standard model by mistake — check which one applies first.
Best for heavy rigs and lube plates
Proven Industries Model PL-5 5th Wheel King Pin Lock
Why it's here
This is the mechanically serious option, and the lube plate clearance is a genuinely useful piece of published information — it is the detail that decides whether a king pin lock closes on a rig it nominally fits, and Proven is the only maker here that addresses it in writing.
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. If pick resistance is part of why you are buying a lock this expensive, the disc detainer is not optional.
Full specifications
| Lock Type | King pin lock |
|---|---|
| Fits | All 5th wheel king pins, including 18-wheelers and the heaviest 5th wheel RVs |
| 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 Proven Industries Model PL-5 product page — construction, cylinder options, lube plate clearance, pricing .
Strengths
- Solid steel welded collar rated by Proven for 18-wheelers and the heaviest fifth wheels
- 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: The lube plate clearance matters more than it sounds. A fifth wheel running a lube plate rather than grease sits with extra material around the pin, and a lock with no allowance for it will not close properly.
Buy it if
Your rig is heavy, you run a lube plate, or you already own Proven locks and want everything on one key.
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
- A third of the price of the premium options
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.
Lightest and cheapest
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 Blaylock King Pin Coupler Lock TL-70 product page — construction, fitment claim, origin .
Strengths
- Aluminum rather than steel, so it is light enough to fit one-handed
- Blaylock rates it for 18-wheelers and the heaviest fifth wheels
- Hardened steel pin securing the collar
- Made in the USA, per Blaylock
- The lowest-cost way to put something visible on the king pin
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: The lightest and cheapest way into this category, and the one where you are buying on the manufacturer's word rather than on published figures. Blaylock lists no pin diameter, no weight, no warranty term and no statement about whether a padlock is in the box.
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 your pin box, not the lock. A lube plate or a sidewinder box rules out most of this category before price enters the conversation. Confirm that first and the shortlist chooses itself.
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?
They stop the opportunist, which is the theft that actually happens to stored fifth wheels. Anyone with a hitch in their truck bed can back up to an unlocked pin, couple, and drive away in under a minute, looking exactly like an owner collecting their RV. A lock on the pin turns that into a visible problem requiring tools and time. It will not stop someone determined and equipped, and no manufacturer here claims otherwise — AMPLock states in its own warranty that it is not an insurer and its protection is "limited and not absolute in case of theft".
What size king pin do fifth wheels use?
Fifth wheel king pins are standardised, which is why most locks in this category advertise fitting everything from RVs up to 18-wheelers. The variable is not the pin itself but what surrounds it — a lube plate, an unusual pin box, or a sidewinder design all change whether a given lock will close.
Will a king pin lock fit over a lube plate?
Only if it was designed with the clearance. A lube plate sits around the pin and adds material a lock has to accommodate; Proven states explicitly that the PL-5 allows for one. If you run a lube plate rather than greasing the pin, check this before ordering — it is the most common reason a king pin lock will not close on a rig it supposedly fits.
What is a sidewinder pin box and does it need a different lock?
A sidewinder or rotating pin box moves the pivot point to improve turning clearance with a short-bed truck. It changes the geometry around the pin enough that AMPLock sells a separate lock for Pullrite and sidewinder-style boxes. If you have one, the standard model is not the one to order.
Should I lock the king pin or the coupler?
On a fifth wheel the king pin is the coupler — it is the single point connecting the rig to the truck, so a lock on it is the whole defence. Bumper-pull trailers are the ones with a separate ball coupler and a choice to make, which we cover in our trailer hitch lock guide.
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.