How we researched this guide
We compared 3 genuine DO35-specific locks, checked Cruisemaster maker pages and manuals, and reviewed owner reports from 4WD in Australia and Track Trailer forums. We did not test any product hands-on; maker claims are reported as maker claims, and owner reports are paraphrased with a link to the source.
No genuine DO35 lock was found on Amazon US, so this guide has no Amazon buttons. Presenting a generic ball-coupler lock as a DO35 lock would be false: a DO35 uses a tow pin, not a 50 mm ball.
The 30-second answer
There are three genuine DO35 locks: the Cruisemaster/Hitchmaster Bi-Lock Security Pin (DO35LOCK), the Kovix DO35 Coupling Lock (KBI-57S), and the TALON D035 Coupling Lock. All three are Australian products, sold through Australian retailers, and none was found on Amazon US. A DO35 lock secures the coupling only while it is unhitched and parked; it does not lock the coupling while you are driving.
| Lock | Suits | How it works | Where sold |
|---|---|---|---|
| Cruisemaster Bi-Lock (DO35LOCK) | DO35 / DO45 | Dummy pin + lock in the joint | AU dealers, eBay AU |
| Kovix DO35 (KBI-57S) | DO35 / DO45 | 18 mm stainless locking pin | AU retailers |
| TALON D035 | DO35 / DO45 v1 only | Brass body, steel pin, registered cylinder | 1KeyCo, Australia |
What a DO35 coupling is, and why ordinary hitch locks do not fit it
The DO35 is a Drop-On 3.5 tonne articulating off-road pin coupling made by Vehicle Components, now Cruisemaster, in Brisbane, Australia. It replaces a standard 50 mm ball with its own tow pin, and it is ADR rated to 3,500 kg. That pin design is the whole point of this guide: a lock made for a ball coupling cannot lock a DO35, because there is no ball to clamp. Any review that shows a generic ball-coupler lock under a DO35 heading is reviewing the wrong product.
The coupling itself has a two-stage ADR-compliant locking mechanism and a Checklock Gen.2 cap on the V3Plus version. The tow-pin nut torque is 440 Nm on the Australian thread and 530 Nm on the US thread, and the maker calls for a maintenance check every 10,000 km or 12 months. None of that is the lock reviewed here. The lock is a separate security accessory that makes the coupling inoperable when the trailer is parked and unhitched.
The one limit every buyer must understand first
A genuine DO35 lock secures the coupling only when it is unhitched and parked. It does not lock the coupling while hitched and driving; that was confirmed by enquiry to Vehicle Components and reported on Track Trailer forums. So the lock is a deterrent against someone hitching your parked trailer and towing it away. It does not stop chain-towing, hitch-swapping, or winching the trailer onto a truck, a point the owner review at 4WD in Australia makes plainly. The same review recommends pairing the lock with a wheel clamp if theft is a real risk where you park.
How to choose a DO35 lock
Match the lock to your coupling version
The TALON D035 suits DO35 and DO45 Version 1 couplings only and is not compatible with the DO45 PLUS. Check your coupling version before ordering any lock, because the three locks are not interchangeable across every DO35 and DO45 variant. The Bi-Lock and the Kovix are both listed for DO35 and DO45 couplings generally, but confirm fitment with the seller for your exact coupling.
Buy from Australia, and plan for it
All three locks are Australian-market products. The Bi-Lock kit was found on eBay Australia (item 397486123222, seller in Padstow, NSW) with a note that it may not post to the United States. If you are outside Australia, expect international shipping, import handling, and a wait. There is no US Amazon listing to fall back on, and that is a fact of this market, not a gap in this guide.
Weigh deterrent value against fiddliness
Owner reports are mixed on ease of use: some owners find the Vehicle Components lock fiddly to lock and unlock, while others find it light, easy to carry, and simple once learned. One reported weak point is the rubber O-ring, which failed in under a year on one owner’s lock; the maker position reported is that the O-ring is an alignment aid only, not structural. Treat the lock as a deterrent for unattended parking, not a guarantee.
The three genuine DO35 locks, reviewed
Cruisemaster / Hitchmaster Bi-Lock Security Pin (DO35LOCK / 18D-DO35-LOCK)
The Bi-Lock is the maker’s own lock. A stainless steel dummy pin drops into the DO35/DO45 universal joint from the top, a lock fits the protruding bottom end, and the coupling becomes inoperable. The kit is a dummy pin, a lock, two keys, and a dust cover. It is listed in the Vehicle Components CIS-16 sheet as the HITCHMASTER DO35 BI-LOCK SECURITY PIN and in the SA Trailer Cruisemaster catalogue as DO35LOCK. This is the lock most DO35 owners mean when they say “the DO35 lock”, and the 4WD in Australia review of it is the most detailed owner account available: light, easy to carry, simple once learned, with the O-ring caveat above. No Amazon listing was found for it.
Kovix DO35 Coupling Lock (KBI-57S)
Kovix lists a lock designed to suit DO35 and DO45 couplings, in 304 stainless steel with an 18 mm locking pin, described as anti-impact, saw and drill resistant, and weather resistant. One Australian retailer page lists it as KBI-50S in the title and KBI-57S in the body, so confirm the part number with the seller before ordering; that inconsistency is a reason to buy from a retailer who will confirm fitment in writing. It is sold through Australian retailers only, and no Amazon listing was found.
TALON D035 Coupling Lock (1KeyCo)
The TALON D035 is Australian-made, with a machined brass lock body, a 316 stainless steel pin, a TALON high-security cylinder registered to the buyer, a black weather cover, and two keys included. Its stated limit matters: it suits DO35 and DO45 Version 1 couplings only, and is not compatible with the DO45 PLUS. It is sold direct by 1KeyCo in Australia, and no Amazon listing was found.
What not to buy instead
A generic tow-bar locking pin can be passed through the DO35 hole as a cheap workaround, and owner sources confirm people do this. But the generic pin is narrower, flops around in the hole, and is far easier to cut than a genuine DO35 lock. A 5/8 inch receiver lock from Amazon is not a DO35 lock, and this guide does not present any generic pin as one. If your budget only stretches to a generic pin, understand that you are buying a visual deterrent, not the fitted lock these three products are.
Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| Lock is fiddly to fit | Pin alignment or O-ring wear | Clean the joint, align the pin by hand, replace a perished O-ring |
| Lock will not engage | Wrong coupling version | Check DO35 vs DO45 PLUS fitment with the seller |
| Trailer still feels stealable | Lock only covers the coupling | Add a wheel clamp; the lock alone is a deterrent |
| No local stock | Australian-only distribution | Order from an AU retailer and allow for international shipping |
Who should not buy a DO35 lock
If you tow with a standard 50 mm ball coupling, do not buy one. A DO35 lock fits a DO35 pin coupling only, and it will not fit your coupling at all.
If you need security while hitched and driving, a DO35 lock will not give it to you. It works on a parked, unhitched trailer. Look at your coupling’s own locking mechanism and your insurance requirements instead.
If you are in the US and need a lock this week, do not count on a DO35 lock. Australian shipping is the only channel found, and it may not post to the United States at all.
Final verdict
The Bi-Lock is the default choice because it is the maker’s own lock with the clearest owner record. The Kovix is the stainless alternative if your retailer confirms the part number. The TALON is the high-security option if your coupling is a Version 1. Whichever you choose, buy it as a parking deterrent, pair it with a wheel clamp, and do not expect it to do a job it was never designed for.
FAQ
What is a DO35 hitch lock?
A lock made for the Cruisemaster DO35 articulating pin coupling. It makes the coupling inoperable while the trailer is parked and unhitched, so nobody can hitch the trailer and tow it away.
Can I buy a DO35 lock on Amazon?
No DO35-specific lock was found on Amazon US in this research. The three genuine locks are sold through Australian retailers and eBay Australia.
Does a DO35 lock work while driving?
No. It secures the coupling only when unhitched and parked. It does not lock the coupling while hitched and driving.
Will a normal hitch lock fit a DO35?
No. A DO35 uses a tow pin, not a 50 mm ball, so ball-coupler locks do not fit it. A generic locking pin can be passed through the hole, but it is narrower, loose, and easier to cut.
Which DO35 lock is best?
The maker’s own Bi-Lock (DO35LOCK) has the clearest owner record. The Kovix KBI-57S is the stainless alternative, and the TALON D035 is the high-security option for Version 1 couplings only.
What is the DO35 coupling rated to?
The DO35 coupling is ADR rated to 3,500 kg. The lock itself is a security accessory, not a towing component, and carries no towing rating.
Does the TALON D035 fit the DO45 PLUS?
No. The maker states it suits DO35 and DO45 Version 1 couplings only and is not compatible with the DO45 PLUS.
Is a DO35 lock enough to stop trailer theft?
No. Owner reports are clear that a lock alone does not stop chain-towing, hitch-swapping, or winching a trailer onto a truck. Pair it with a wheel clamp.
Sources
- Cruisemaster DO35 V3Plus product page
- 4WD in Australia — DO35 Hitch Lock Review
- 4WD in Australia — DO35 Hitch review
- Track Trailer forums — DO35 lock discussion
- 1KeyCo — TALON D035 Coupling Lock
- Caravan Mods — Kovix DO35 Coupling Lock
- SA Trailer Cruisemaster catalogue (DO35LOCK)
By Leo, Founder, WinchInsider
Leo covers towing, recovery and workshop gear for WinchInsider, working from maker specifications, manuals and owner reports.