Use the extra-long shank to thread deep and hard-to-reach holes. These taps are made of uncoated high-speed steel and are for use on most metal and plastic. With a square shank, they're compatible with tap wrenches and tap holders for drill presses and milling machines. All have a plug chamfer with 3-5 chamfered cutting threads, so they're suitable for start-to-finish tapping. When using them to tap closed-end holes, be sure to leave sufficient space at the bottom for chips to accumulate.