This is a genuine OEM screw replacement sourced directly from the manufacturer. It is a muffler stud screw used on lawn mowers, snowblowers, and other outdoor lawn and garden engines. This muffler screw attaches the muffler to the engine. These screws go directly through the muffler case and into the engine housing. There is no need for a nut or other fastener. Over time, vibration from the engine may cause them to loosen and possibly fall out. If this happens, the muffler can fall off. Periodic inspection and tightening will prevent this from occurring. A visual inspection as well as checking the tightness by hand will reveal any issues.If the screws are missing or rusted and need to be replaced, make sure the muffler has cooled before attempting to remove the screws. Use a wrench to remove the screws from the muffler. Insert the new screws and hand tighten. Use the wrench to tighten slightly more. Be careful not to overtighten and strip the screws. These screws are 1/4-20 x 2-9/32, gold in color, and sold individually. These muffler shoulder screws are compatible with lawnmowers, snow blowers, chippers, edgers, pressure washers, and other engines manufactured by MTD, Craftsman, Tecumseh, Toro, and Cub Cadet.