Pedro's Bottom Bracket Socket Description: Professional quality with a precision fit to properly install, remove, and adjust Shimano, ISIS, and other splined 20-tooth cartridge-style bottom brackets. A square 3/8" drive allows for mechanical advantage with a torque wrench. Features: Fits all Shimano and ISIS Drive splined 20-tooth bottom bracket cups and other cartridge bottom brackets Fits square 3/8` drive, and works with Pedro`s snap-channel Pro Socket Handle, 24mm socket or wrench, or in a bench vise Professional quality, precision sized for the perfect fit