Brand: Automotive Racing Products (ARP)
These hardened, parallel-ground chrome moly washers have a special "insert" design that fits into an oversized hole to help support and protect the material around the hole. This protection is especially critical in applications such as aluminum cylinder heads, where torquing the head bolts could force the aluminum to collapse into the hole. Holes which see radial forces (such as motor mount plates) will also benefit from these hardened inserts.
This size fits 5/16" bolts and has an oversized 5/8" (0.625") OD. The hole must be bored to 0.380" ID (9.65mm) to accommodate the insert. Black oxide finish. Sold individually.
