The park tool bbt 4 bottom bracket tool 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 park tool bottom bracket tool features the bbt 4 is compatible with the following sealed cartridge bottom brackets campagno