This OEM 5/16" Lock Nut is constructed of metal and comes individually sold. It requires a wrench set and socket set to use. This nut will secure parts into place, and should be replaced if damaged. Refer to your make, model and diagrams to check if this size is correct.
This is an authentic Toro replacement part, sourced from the original manufacturer for use with snowthrowers. The metal washer is commonly used to disperse pressure put on the auger housing by the nut that fastens the chute retainer across a wider surface area. This bolt is sold individually.