The original centerlock rotor shim - tested and perfected since 2016. Comes pre-slit for perfect, seamless installation. No additional work required, just install and ride. Use for precise alignment of your disc brake hub rotors to make switching wheels a snap. Pack of 4 stainless shims, each shim is .25mm thick. For centerlock hubs/rotors. We recommend a maximum of 4 shims per hub to maintain sufficient thread engagement between lock ring and hub. Also, if your rotors are more than 1mm off from hub to hub, something is probably amiss.