Allstar ALL18215 3/16" I.D - 1" O.D Steel Back Up Washer, (Pack of 100) Steel back up washers have a 3/16 inch i.d with a 1 inch o.d. Back-up washers provide added strength when fastening panels together or when re-securing damaged panels Several other popular sizes are also available and are sold separately One set of 100 pieces It has a 90 day limited warranty