360 degrees of solid steel protection against trailer theft. The UMAX50 is constructed of solid hardened steel and fits most coupler sizes (1 7/8″ to 2 5/16″). a 5/8″ (16mm) hardened steel shackle helps ensure your trailer is secure, even when left unattended. It has a patented dual locking system and a rust proof hammer tone epoxy finish for extra security.