Park tool bottom bracket tool bbt4the bbt 4 is made for the installation and removal of 6 notch sc s and ac h cartridge cups used on sealed cartridge bottom brackets these bottom brackets have six notches around the outside of each cup the handle of the bbt 4 is vinyl coated for comfort the major diameter of the tool is nominally 44mm and the minor diameter 38mm compatibilitycampagnolo veloce xenon mirage daytona avantibuy park tool bb tools from chain reaction cycles the worlds larg