This Proven Industries 400A blue puck lock is used with the 2516 and 2178 coupler locks. Keyed alike. Features a hidden shackle, and includes 2 keys. Aluminum construction with a 6 pin brass cylinder. When used as part of the Proven Industries 3 part coupler lock, it prevents theft by securing not only the coupler but also your safety chains. Made in the USA. 90 day warranty