These Speed-up shims influence the length of the variator sleeve. Lengthening can improve acceleration and shortening can increase top end speed. Measure the length of the sleeve before installing the length of your choice. Kit contains 30 Control shims with 10 of each of the following: 0.1mm, 0.2mm and 0.5mm thick. When using tuning variators, measure the external diameter of the variator sleeve. This should be 18mm