"HEAD DIA:0.75""; BASE DIA:0.7812""; CONVERTS:0.375"" SQUARE TO 0.25"" HEX.; ADAPTS STANDARD SQUARE DRIVE CHUCKS TO 1/4"" HEX DRIVE CHUCKS THAT ARE COMPATIBLE WITH IMPACT DRILLING ACCESSORIES; PATENTED JAW DESIGN IN COMPATIBLE WITH ALL 1/4"" HEX SHANK ACCESSORIES INCLUDING INSERT BITS; LARGE CHUCK WITHSTANDS HIGHER TORQUE DEMANDS OF IMPACT DIRVERS"