Trimax SP125 The SP125 is a 1/2" pin which fits all Class I and II receiver hitches. Features hardened steel construction with a triple chrome plated finish. Non-locking receiver pin. A receiver pin is used to secure the receptable part of a trailer hitch (attached to a vehicle) to inserts such as ball mounts, drawbars, accessory carriers or ornamental receiver plugs. The most common receiver pins are 1/2" and 5/8" in diameter. Class II receiver hitches have 1-1/4" receptacles and use 1/2" pins. Class III, IV and V receiver hitches have 2" receptacles and use 5/8" pins. TRIMAX makes the world's toughest locks. Through value added engineering design, TRIMAX is committed to product innovation that holds up to the highest quality standards. TRIMAX provides maximum security for marine, trailer and tow, RV, performance truck, power sports and bicycle applications. Tested. Tough. TRIMAX..