The BBT-79 is a precision machined aluminium tool for the installation & removal of 12-notch external bearing bottom brackets with an outside diameter of 46 mm The BBT-79 fits Race Face Cinch Zipp Vuma Rotor BSA30 Hawk Racing BB3086 & others 3/8 inch ratchet/torque wrench drive compatible Made in the USA & covered by Park Tools legendary limited lifetime warranty