Master Lock Trailer Coupler Lock for 1-7/8", 2" & 2-5/16" Couplers - Red, Corrosion-Resistant Zinc

The Master Lock 389DAT is a universal trailer coupler lock designed to fit most 1-7/8", 2" and 2-5/16" couplers and deliver visible, corrosion-resistant hitch protection.

This bright red coupler lock offers an easy-to-install way to deter unauthorized hitching and theft for utility trailers, campers, RVs and boat trailers. Built from zinc with an advanced internal locking mechanism, the 389DAT balances everyday weather resistance with mechanical security. It ships with two keys and a compact form factor so you can store a spare key with your trailer accessories.

How does this lock fit different trailer coupler sizes?

The 389DAT uses a universal design sized to engage common coupler openings used on consumer trailers. It accommodates 1-7/8" (48 mm), 2" (51 mm) and most 2-5/16" (59 mm) couplers, so one lock covers many towing setups without adapters.

• Works on most standard coupler throat diameters for common trailers.
• Single-piece installation slides into the coupler and locks closed for quick use.
• Spares needed only if you use multiple trailer types at the same time.

How secure is the Master Lock 389DAT against tampering?

This model includes an advanced internal locking mechanism engineered to resist picking and basic prying attempts. The visible bright red finish also acts as a deterrent by signaling that the trailer is secured.

• Internal components reduce vulnerability to simple picking techniques.
• Zinc construction increases rigidity versus cheaper plastic options.
• High-visibility color helps discourage opportunistic theft.

Will the lock hold up outdoors and in wet conditions?

The lock's zinc body provides corrosion resistance for regular outdoor exposure, making it suited for marina, campsite or driveway use. Routine maintenance—wiping and occasional lubrication of the keyway—will help preserve smooth operation over time.

• Zinc finish resists rust better than uncoated metals in damp environments.
• Compact design reduces trapped water and dirt after exposure.
• Two included keys let you keep a spare to avoid getting locked out during trips.

What makes this lock easy to use day-to-day?

Installation is straightforward—slide the lock into the coupler and engage the key-operated cylinder. Its compact shape stores easily with other hitch accessories and the included spare key provides practical redundancy.

• Keyed operation is fast and intuitive for frequent attachment checks.
• Bright color makes the lock visible when checking trailer readiness.
• Lightweight, compact form is convenient for transport and storage.

Who is this for: The Master Lock 389DAT is a practical choice for trailer owners who want a visible, easy-to-use coupler lock that fits the most common coupler sizes. It's well suited for weekend boaters, RV and camper owners, small-business fleets, landscapers and anyone who leaves trailers at a campsite, marina, jobsite or driveway and wants an effective theft-deterrent without complex installation. Backed by Master Lock's limited lifetime warranty, it provides everyday protection for towable equipment where compatibility, visibility and corrosion resistance matter.