Universal compatibility fits A-frame and straight bolt-on 2-inch trailer couplers for broad usability
Patented Cobra tubular keyway system provides high-security, tamper-resistant access control
Fits most standard S-hook style safety chains for versatile trailer attachment
Hardened steel construction ensures durability and long-lasting performance
Manual operation allows for easy, tool-free installation and removal
Description
Model 2178 is our most popular trailer coupler lock because it fits the most amount of trailer couplers on the market. From an "A-frame" welded-on trailer coupler, to a straight bolt-on style trailer coupler, Model 2178 fits them both and will provide the most secure trailer coupler lock available.
Designing the best coupler
Material
Hardened steel, aluminum, plastic
Lock Type
7-pin tubular lock (Cobra standard, upgraded at no extra cost)
Compatibility
Fits most 2-inch trailer couplers (A-frame and straight bolt-on)
Key System
Cobra patented tubular keyway
Operation
Manual, mechanical
Color
Black, blue
4.8
1.1K ratings
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Great improvement from the older model
I just got the new model 2178 for my new boat trailer and it’s a way better improvement from the older model I got since it wouldn’t hold my safety chains in the lock as designed.
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Peter · 8 days ago
Great Quality for extra piece of mind
Expensive? Yes. Worth it? Absolutely!! This lock is built like a tank! It’s super heavy duty and I have total faith that it would hold up to or deter a possible thief. Plus they have amazing customer service and support. I highly recommend a Proven Lock. You will not be disappointed!
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Bradley · October 28, 2026
One Flaw - Great Locks
This company is fantastic; but there is one flaw in the design, the puck lock is very difficult to unlock because the key is inserted from the bottom, which is nearly impossible for especially myself. I understand it protects from weather but again the design could be best if worked from side. Otherwise it is great to keep my two trailers exactly where I put them.
