Blade adapter used on AYP 20" and 22" walk behind mowers. Genuine FSP part 850977. Adapter part numbers 851514 and 193825 change to 850977. This is the blade adapter that the nubs shear off when you hit something. Designed to break so it is less likely to damage the crankshaft when something is hit.
Item# : SPM574295614
Model # : 850977