The park tool sbc 1 spoke bearing and cotter gauge is ideal for sizing spokes ball bearings and crank cotters to use just hang the head of the spoke in the oblong hole and read its length on the scale for crank cotters and ball bearings it works just like a gauge for drill bits park tool sbc 1 spoke bearing and cotter gauge features a convenient aid for confirming the size of common bicycle parts fit the head of the spoke in the oblong hole and read its length o