A spark plug wrench is a universal tool needed by anyone who is going to mow lawns on a consistent basis because spark plugs should be replaced at least annually. This is not only to maintain good working compression in the mower but to keep optimum fuel/air mixing in the carburetor. Mowers work more efficiently and last longer with good spark plugs. There are several warning signs to watch for in order to determine whether or not it's time to replace a spark plug. Difficulty in starting the engine or loss of power without the motor completely dying are two signs that a plug needs to be replaced. After it has been determined that a plug is bad and needs to be replaced, it's wise to look at the bottom of the plug where it sits in the cylinder to see what wear there might be. Watch for oil or gasoline deposits, as these signal serious problems. A burnt electrode or one that is fouled with carbon may indicate carburetor issues that need to be addressed as well. This plug wrench fits both 3/4 and 13/16 sized plugs and is OEM certified as a genuine replacement part. This part will work with lawn mowers, snowblowers, tillers, pressure washers, leaf blowers, edgers, generators, wood chippers, and other small engine lawn equipment made by Briggs & Stratton, Craftsman, Toro, Murray, Wheel Horse, Lawn Boy, and Simplicity.