These handy washers are made to protect the top of holes from galling or collapsing around studs or bolts. They’re ideal for head bolt holes, mid-motor plates, or any other high-wear area that requires a washer. Easy to install by just oversizing hole and pressing in washer. ARP Insert Washers are fully CNC machined from premium thru-hardened 8740 stock. PartNumber : arp400-8551 Description : Insert Washer; Single Piece Material : Stainless Steel OD : 0.79 Insert Size (ID/OD) : 10mm / 0.5 Engine Components::Hardware - Singles