ARP's handy thread cleaning chaser taps are designed with correct thread pitch and diameter to clean dirty blind or thru holes. Taps come in five SAE sizes 1/4", 5/16", 3/8", 7/16", 1/2" . Please note that these are stricktly cleaning taps and not designed to cut thread. They are a handy addition to the tool box of any serious engine builder and an essential aid for preparing any block for final assembly. Don't take a chance on improper torque values caused by dirty threads! Use these handy thread chasers whenever possible!