B137980 Bar-groove Cleaner/Piston StopOne New Aftermarket Replacement Bar Groove Cleaner and Piston Stop for Chainsaws and 2 Cycle Outdoor Power Equipment This dual function chainsaw service tool serves two essential maintenance purposes. The bent end inserts into the spark plug hole to stop piston movement, making flywheel and clutch removal safe and easy. The opposite end works as an effective bar groove and oil hole cleaner to maintain proper lubrication flow to the bar and chain.