Forney 60124 Tungsten Carbide Burr with 1/4-Inch Shank, Tree Radius, 1/4-Inch This are easy to use This are highly durable This is manufactured in United States Shank mounted tungsten carbide burrs are double cut for fine work Designed for use on ferrous metals, plastic, fiberglass and other machinable materials Great for deburring, sculpting and removing material in hard to reach areas Designed for use with high speed die grinders Max RPM is 70,000