The park tool bbt 29 bottom bracket tool is a double ended bottom bracket wrench designed to fit 16 notch bearing cups with an outside diameter of 39mm eg shimanoreg dura acereg 9000 series and xtrreg 980 series as well as 16 notch bearing cups with an outside diameter of 485mm eg fsareg megaevoreg park tool bbt 29 bottom bracket tool features the bbt 29 is a double ended bottom bracket wrench designed to fit non standard diameter 16 notch exte