5/16 in. x 3-1/8 in. Star Drive Washer Head Rugged Structural Wood Screw (45-Pack)GRK Fasteners RSS screw is made from Climatek coated and hardened steel. Its sharp threads and point bite instantly into material (including hardwood), reducing the splitting effect caused by smaller shanks. Its washer type head has no sharp edges like conventional lag screws and the added shoulder underneath the washer has the ability to center the RSS screw in predrilled hardware. Ideal for ledger boards and more Self tapping May be used as a lag