It is a prop adaptor I made. I cut the head off an 8 x 1.00 bolt and set it in the adaptor with locktite. The nut is the stock Poulan nut from the flywheel, it is larger than other available nuts. I did it this way because the stud won't wear the threads in the aluminum and I won't have to be as carefull tighting the prop nut. Also way easier to mount a spinner adaptor.