The Hillman Group 300306 5/16-Inch Split Lock Washer Grade 8, 100-Pack
This split lock washer provides a circular bearing surface with offset split ends which help bite into the mating material to provide a locking feature when tightened beneath a nut. It is round with a hole in the center and can be used where loosening from corrosion or vibration is a concern. Lock washers are commonly used in any application using a bolt where two pieces are being drawn together.