Lock nut with nylon insert.
Lawn mower flywheel key (woodruff key). The flywheel key aligns the flywheel in the correct position on the crankshaft. If the engine stops suddenly due to hitting a hard object, the flywheel key shears in half to prevent damage to the engine. If the flywheel key is broken, the engine won't start.
Nylon insert locking nut. Used as part of the shear bolt assembly, as well as other locations within the equipment.
Spacer-part of the shear pin assembly used on Toro snowblowers. Replace as an assembly.