Trimax Coupler Locks - A coupler is the forward most part of a trailer tongue that envelopes and secures to the tow vehicle hitch ball. The lever on the coupler both allows the ball to be received into the coupler and prevents the ball from being removed. Accordingly, a coupler lever lock prevents the lever from moving into the open position.These coupler locks are available in 3 different sizes- 7/8 in, 2.5 in, and 3.5 in. Machined Hardened SteelTriple Plated Chrome Finish