This pinion sprocket lets you drive your 8mm pitch chain in an assembly. It press-fits onto an 8mm REX shaft. The snug fit means you do not need to axially constrain the sprocket in most cases. The built-in shims on either side of this sprocket allow it to be pressed right up against a bearing without binding the inner and outer races or needing a separate shim. The acetal makeup of this part means it will be low-friction with excellent wear characteristics.