5/16 in. x 4 in. Star Drive Round Head Rugged Structural Wood Screw (45-Piece per Pack)GRK's RSS screw is made out of Climate 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 screw