Trimax Receiver/Coupler Lock Set 3 1/2in 3-1/2in. The adjustable 5/8" steel sleeve prevents rust and spins to prevent cutting fitting class III V and V hitches. The lock head can't be false locked or "pop" open. Lock it or lose it Features of Trimax Receiver/Coupler Lock Set 3 1/2in 5/8" Class III receiver Trimax Lock's exclusive internal O-ring and watertight cap seal out moisture The round key won't bend or break like flat keys and are impossible to pick Adjustable stainless steel coupler pin fits 7/8" 2-1/2" and 3-1/2" coupler spans Package Contents: Trimax Receiver/Coupler Lock Set 3 1/2in Trimax TM3123: Receiver/Coupler Lock Set 3 1/2in 3-1/2in