Box of 25 of 1/2"-13 x 2 1/2" Black Oxide Alloy Steel Socket Cap Screws - Holo-Krome The more boxes you buy the better deal when can give on the buy it now. Specifications: Diameter      1/2" Length          2-1/2" Thread          Size 13 Thread          Coarse Drive Size     3/8" UNSPC Code 31161518 Type Socket Cap Screw Material        Alloy Steel Finish Black Oxide Drive            Hex