The Grainger 5/16"-18 internal threading tap is made of high speed steel with a spiral flute design. It has a taper length of 3/4", an overall length of 1-1/4", and a square shank drive. This tap is designed for hand tapping applications in low carbon steels, cast iron, brass, aluminum and plastics. It creates 5/16"-18 internal threads for fastening and repair applications. The tap has a bright finish and meets ANSI standards for fit and tolerance.