PurposeUsed to adapt "keller" ratchet drive wrench to multiple nut sizes of the ratchet drive wrenchUsed WithKeller ratchet drive wrenchWrench Size5/16Opening Shape12Wrench End TypeSocketWrench Body TypeStraightWrench VariationStandardDrive TypeExternal HexDrive Size3/8Head Outer Diameter0.50Overall Length0.87