These gems are machined to precisely fit the preload adjuster cap on all modern 24mm spindle Shimano cranks. The finger spline offers good leverage to install, remove or adjust the preload cap. We also added a 5mm hex in the center should you need a little extra leverage that a hex key provides. These are also compatible with our fit kits and with the addition of the 8mm or 10mm saddle height bullets for a more accurate measurement of saddle height.