Wolf Tooth bottom bracket sockets are tools for installation and removal of external cup bottom brackets. They are machined here in Minnesota with aircraft grade aluminum. Large finger notches so you can start threading the cups by hand 3/8" square socket or 1" hex for ratchet/torque wrench Most sockets have either a Shimano bearing preload tool or a 16mm hex for use with Race Face Cinch cranksets Steel inserts for magnetic coupling compatibility with the Pack Wrench   Compatibility BBS3916: 16 notch BB socket for 39mm diameter notch pattern, Shimano 9000 series, DURA-ACE, BB92, XTR BB93 BBS4116: 16 notch BB socket for 41mm diameter notch pattern, Shimano 105, Ultegra BBR60 and 6800, XT MT-800 BBS4416: 16 notch BB socket for 44mm diameter notch pattern, Shimano BB80, BB5700, BB70, BB51, Enduro T47, Wheels T47, many from Hollowtech II, Campagnolo, Chris King, FSA MegaExo, Hope, SRAM/Truvativ GXP, Race Face X-type, Surly, and more BBS4612: 12 notch BB socket for 46mm diameter notch pattern, BB386, Race Face 30mm Spindle, TF47, SRAM DUB, RaceFace Cinch, Zipp Vuma, Rotor BSA30, Hawk Racing BB3086, Cane Creek Hellbender, and more.  BBS4816: 16 notch BB socket for 48mm diameter notch pattern, FSA 386 MegaEvo, Wheels PF30, BSA30, BB386, and more BBS4912: 12 notch BB socket for Praxis T47IB BBS5212: 12 notch BB socket for Chris King T47 BBS5216: 16 notch BB socket for DUB T47.