You are looking at a Loc-it Demco EZ-Latch style coupler lock. This lock fits Demco style EZ Latch channel and A frame 2 " CAST couplers only. This will fit couplers 3 1/2" and under for the max width. These are of Heavy-Duty Steel Welded Construction. The locks are bolt cutter proof. The only way to remove this lock is by cutting torch and electric cutting tools. The square housing is where the locking to the coupler is done. This will be secure even if slide is in the open position. This is a very secure lock for these couplers. The housing is just under 3/8" and comes with puck lock and is enamel painted. Can be repainted your color. Comes with a 90 warranty from the manufacturer to cover manufacturing defects. There is FREE SHIPPING to the lower 48. This will not fit "Stamped Metal Couplers" only Cast Couplers as shown....Channel, stand, and coupler are for display ONLY, the sale does not include these mentioned. NO INTERNATIONAL SHIPPING...PLEASE