The USE shim system allows you to fit a post into virtually any frame size. The shims are made to 100mm length and are longer than other shims on the market. This gives your seat post much better support inside the frame. All shims are designed with a "top lip" to stop the shim sliding into the frame. Rolled Aluminium shim - the very thinnest shims are rolled from sheet metal. 25.4mm shims need to be so thin as they are etched down in acid to the correct tolerance and are too thin to anodise - Machined to very high tolerances from 6082 T6 Aluminium and then black anodised to protect from corrosion - 100mm length - 'Top lip' to stop shim sliding into frame