1.385in ID with 3/16in and 1/4in keyways. Engine work requires repeated crankshaft rotation. This non-marring, aluminum tool rotates the crankshaft the proper way, when the balancer is off. Making sure to have the proper size, position this socket over the end of the crankshaft, so it can be turned using a 1/2in breaker bar or drive ratchet.Proform Engine Crankshaft Turning Socket Tool 66900Specifications: Feature/Benefit 1.385 inch ID with 3/16 inch and 1/4 inch keyways. Tool Type Turning Sockets & Nuts Category Crank Turning Socket Description_ABR Crank Socket Description_SHO Crank Turning Socket Description_INV Crank Socket Description_INV SB Ford Description_INV Buick Description_INV Pontiac Description_DEF Engine Crankshaft Turning Socket Tool Description_ASC Engine Crankshaft Socket Description_ASC Fits SB Ford Description_LAB Engine Crankshaft Socket Description_LAB Fits SB Ford Description_DES Engine Crankshaft Socket Description_DES Fits SB Ford Description_EXT Engine Crankshaft Socket Description_EXT Fits Small Block Ford, Buick and Pontiac Engines Description_EXT Fits 1.385 ID Crank Snout with 3/16 In. and 1/4 In. Keyways Description_EXT Made from Aluminum Description_EXT Natural Finish Description_EXT 1/2 In. Drive for Use With Breaker Bar or Drive Ratchet Description_EXT Sold Each Description_MKT 1.385in ID with 3/16in and 1/4in keyways. Engine work requires repeated crankshaft rotation. This non-marring, aluminum tool rotates the crankshaft the proper way, when the balancer is off. Making sure to have the proper size, position this socket over the end of the crankshaft, so it can be turned using a 1/2in breaker bar or drive ratchet.