This is a pack of ten ProTek R/C 3x8x0.5mm Clutch Bell Stop Washers. These washers have a 3mm inner diameter, with a 8mm outer diameter and are 0.5mm thick. These can be used in a variety of applications, but are an excellent choice to use as a stop washer on the end of an engine crankshaft to hold the clutch bell and clutch shims in place.