This tool is required to remove the clutch from certain model saws. This means you will need this tool to replace your clutch and drive sprocket. Each tool has a 19mm nut fitting so you can easily adapt a socket or bar wrench to torque. Clutches are reverse threaded, so be sure to turn the proper direction. A piston stop will help. This three pronged tool is for certain model Echo chainsaws, but be sure to check if you have three springs on your clutch. It will also work on some Husqvarna and Jonsered saws also.