Master Lock Trailer Hitch Coupler Lock 379ATPY Black — Keyed Zinc Security, Fits 1-7/8″, 2″ & Most 2-5/16″ Couplers

The Master Lock 379ATPY is a keyed trailer hitch coupler lock that secures 1-7/8", 2" and most 2-5/16" couplers with a heavy-duty, pick- and pry-resistant mechanism.

Protecting a trailer, RV or tow vehicle starts at the coupler; the Master Lock 379ATPY offers straightforward, durable security with a universal fit. Constructed of zinc to resist rust and corrosion and backed by Master Lock’s limited lifetime warranty, this compact lock ships with two keys and installs without tools to give owners quick, reliable deterrence against theft.

How does this lock fit different trailer coupler sizes?

The 379ATPY uses a universal insert and locking shank engineered to engage the common coupler diameters used on trailers and RVs. It’s shaped to slide into the coupler cavity and lock in place, preventing the latch from closing around a ball or from being removed.

• Compatible with 1-7/8" (48 mm), 2" (51 mm), and most 2-5/16" (59 mm) couplers
• Single unit design fits a wide range of standard couplers without adapters
• Simple push-and-lock installation—no tools required

What makes the locking mechanism secure against tampering?

Master Lock engineered the 379ATPY to resist common attack methods like picking and prying by using a reinforced locking mechanism and robust internal components. While no lock is invulnerable, this model raises the time and effort required to defeat the coupler, making theft less likely.

• Advanced internal tumblers and reinforced housing reduce picking risk
• Zinc construction adds structural strength and corrosion resistance
• Low-profile shape minimizes leverage points for pry tools

How weatherproof and durable is the Master Lock 379ATPY?

The lock is built from zinc with finishes designed to stand up to outdoor storage and seasonal use. The materials and design limit rust and wear so the lock stays functional through rain, salt air and road grime.

• Zinc body resists corrosion for longer outdoor life
• Sealed components reduce moisture intrusion into the lock core
• Includes two keys so you have a spare for routine use

Can I trust the warranty and support for this product?

Master Lock includes a limited lifetime warranty that covers defects in materials and workmanship under normal use. If the lock fails due to a covered defect, Master Lock’s support and warranty process provides repair or replacement options consistent with the warranty terms.

• Limited lifetime warranty from an established security brand
• Customer support available through Master Lock for warranty assistance
• Warranty covers manufacturing defects, not damage from misuse

Who is this for: The Master Lock 379ATPY is ideal for trailer owners, RV enthusiasts and anyone who frequently parks or stores a trailer, camper or utility trailer and wants a simple, durable deterrent at the coupler. It’s best for users who need a universal, no-tools solution built to resist weather and typical tampering, and who value a trusted brand warranty and an included spare key.