This is a genuine replacement screw designed for use in select MTD engines on lawn and garden equipment. Specifically, this is an anti-rotation screw, which is used to stop the drive shaft housing from turning inside of the main housing assembly. This screw is a small part that is subject to constant vibrations, pressure, and high temperatures. It can sometimes become worn or damaged as a result or even break off entirely, which would mean that the inner housing would no longer be held in place accordingly. If this screw is damaged or lost, it needs to be replaced with a genuine OEM replacement as soon as possible. This MTD anti-rotation screw is manufactured with high-quality materials and designed for use in select trimmers from MTD, RYOBI, Yard-Man, Troy-Bilt, Murray, Cub Cadet, Yard Machines, and Bolens. This replacement will require a screwdriver. Simply remove the damaged screw, if it is not already missing, from the clutch cover assembly, and then install the new screw. It should only take a few minutes to perform the replacement. Be sure to wear gloves to protect the hands. This screw is sold individually and does not include any additional parts or hardware.