Bottom bracket shell widths vary slightly between frames even when they follow the same standard, and this wave washer compensates for those variations when you install Campagnolo Ultra-Torque, Power-Torque, or Over-Torque cranksets. The wavy profile compresses when you tighten the crank bolt to the specified torque range, which creates bearing preload while still allowing the bearings to spin freely. Without this washer, you risk over-compressing the bearings if your frame's shell sits at the narrow end of the tolerance range, or leaving excessive play if the shell runs wide.

The washer installs on the non-drive side between the bearing and the bottom bracket cup. You slide it over the left crank's spindle so it seats against the bearing face, insert the crank arm into the shell to mate with the drive-side crank at the Hirth coupling, then thread the fixing bolt through the hollow left arm and tighten to the coupling. When torqued properly between forty-eight and sixty newton-meters, the wave washer absorbs the dimensional variations while maintaining proper bearing function. The stainless steel construction handles the compression loads without taking a permanent set that would compromise bearing preload over time.