Designed specifically for boat building, these Silicon Bronze screws have cut threads and the full-body-diameter shank preferred by boat builders. Unlike our rolled thread steel screws with their reduced shank, the shank diameter below the head is the same diameter as the outside of the threads. This completely fills the clearance hole normally drilled for the shank, thus creating a seal. Made of marine grade alloy 651 Silicon Bronze for dependable corrosion resistance. Remember to drill a body hole for the screw shank, and a pilot hole for the threads. All screws are threaded for 2/3 of the shank. Made in China.