Master Mechanic, 789147, 1/4 - 18 NPT Plug Tap, For Cutting Internal Threads, Standard, Pipe & Metric Sizes, Tough, Carbon Tool Steel For Long Life, Resists Rust & Tarnish, 4 Flutes For Extra Chip Clearance, Right Hand Threaded Taps In Plug, Taper & Bottoming Styles, Drill Size Permanently Marked On Each Tap, Carded.