Race face isis srxwith an m15 chromoly spindle and single row double sealed cartridge bearings the srx was designed for the all around rider looking for solid performance at a reasonable price the srx is also compatible with e type derailleurs isis drive m15 chromoly spindle shot peened finish for strength forged and cncd aluminum cups and reinforcing sleeve single row double sealed cartridge bearings 64 ball bearings in each bottom bracket adjustable cups fit 68 and 73mm shells fixed cup o