How can anyone even  write twenty words about a flywheel key?  It's an oem rectangular slab of metal designed to break at a certain amount of stress, and hopefully not smear up the works too much in the process.  It came quickly, it fit,and  the mower still doesn't work. The great thing is, if you have prime, you don't have to waste time (finding and) traveling down to a well stocked enough store, so if you're not going to get around to it until next weekend anyway, its' a no-brainer.