The Oregon Sure Sharp kit includes three sharpening stones. You want to use the largest stone that fits at the correct angle, which is parallel with the top of the tooth. My chain can fit the smallest stone, but it does not contact the entire tooth, so I will be using the middle stone for my chain. You want the stone to contact the entire tooth to avoid creating a shelf underneath the cutting edge. Remove the guide plate to install the grinding stone. Press the detent to stop the collet from turning, and tighten the collet.