Master Lock Trailer Coupler Locks — Universal Fit 1-7/8, 2, 2-5/16 in | 2-Pack Bright Red, Keyed-Different

Master Lock 389DAT universal coupler locks are heavy-duty trailer coupler locks that fit 1-7/8", 2" and 2-5/16" couplers to deter tow-away theft and make securing your trailer quick and visible.

These two keyed-differently coupler locks from Master Lock are built to fit the most common trailer ball coupler sizes — 48 mm (1-7/8"), 51 mm (2") and 59 mm (2-5/16"). With an engineered internal locking mechanism and a bright red finish, the set is engineered to be easy to install, corrosion resistant, and a clear visual deterrent when your trailer is unattended. The locks are sold as a pair, each with a unique key, so you can secure multiple trailers or keep a spare while avoiding keyed-alarms between units.

How does this lock fit different coupler sizes?

The Master Lock 389DAT uses a universal internal geometry that accommodates the common range of ball-coupler diameters. The lock slides into the coupler throat and latches in place, preventing the coupler from closing around the hitch ball. Its design requires no tools for installation or removal.

• Fits 1-7/8" (48 mm), 2" (51 mm), and 2-5/16" (59 mm) couplers
• Designed to seat securely inside the coupler opening
• Tool-free installation and quick removal
• Sold as two locks, each keyed differently

What level of theft protection can I expect?

This lock adds a physical barrier and visual signal that discourages opportunistic theft and tow-away attempts. The internal advanced locking mechanism resists common picking and prying attempts better than simple pin locks. While no lock is completely impervious, this product raises the effort and time required to access the coupler, which deters most thieves.

• Advanced locking mechanism resists picking and prying
• Bright red finish acts as a visual deterrent
• Solid construction increases removal time for thieves
• Pair configuration lets you secure two trailers or keep a spare

How does it stand up to weather and regular use?

Master Lock designed the 389DAT to resist rust and corrosion so it remains functional in outdoor, trailer-ready environments. The exterior finish and internal materials limit degradation from exposure to moisture and road salt. Regular inspection and basic maintenance will extend service life like any outdoor security hardware.

• Corrosion-resistant materials reduce rust over time
• Durable finish withstands outdoor storage and travel conditions
• Simple mechanism makes cleaning and lubrication straightforward
• Built for frequent installation and removal cycles

Is this easy to install and use daily?

Yes. The unit is designed for quick, tool-free installation that takes seconds to secure the coupler when you park. Removing the lock is similarly fast with the correct key, making it practical for frequent trailer hookups without extra hassle.

• Insert into coupler throat and rotate/lock in place
• Comes ready to use out of the box with two unique keys
• No special tools or mounting hardware required
• Compact form factor stores easily when not in use

Who is this for: The Master Lock 389DAT two-pack is ideal for small-business owners, recreational vehicle owners, contractors, landscapers, and anyone who parks trailers unattended and wants a practical, visible, and weather-resistant way to deter theft. It works well if you need a universal, easy-to-use lock that fits the most common coupler sizes and prefer having two uniquely keyed units for separate trailers or a spare.