Park tool bottom bracket tool hollowtech iithe bbt 9 is used to remove and install external bearing bottom brackets one end of the bbt 9 securely engages the 16 notches of the bottom bracket cups the other end of the tool engages the 8 internal splines of the crank arm adjustment cap the bbt 9 fits cups and lock rings with 16 external notches and an outside diameter of approximately 44mm features works with many external bearing crankset bottom brackets including shimano hollowtech ii c