Universal Joint is a coupler interposed between Bi-Hex socket and the driving tool. It is useful for tightening nuts located at difficult angular positions, which cannot be reached with standard tools. This is available in 1/4" (6.35 mm), 3/8" (9.5 mm), 1/2" (12.7 mm), 3/4" (19 mm) and 1" (25.4 mm) square drives. Â