TRIMAX (UMAX100): Premium Universal Solid Hardened Steel Trailer Lock July 31, 2015July 31, 2015 David Ayers Industry, News Premium universal lock offers 360 degrees of solid, hardened-steel, dual-purpose coupler security (fits most couplers). Hardened 5/8″ (~16 mm) steel shackle Key hole cover slides up to seal out dirt Huge 7-tooth 3/8″ locking-lug system Ballistic-grade nylon housing protects against the weather and absorbs hammer blows TRIMAX_UMAX100