3/8", SF-3, Tree Radius, Tungsten Carbide Burr With 1/4" Shank, Shank Mounted Tungsten Carbide Burrs Are Double Cut For Fine Work, Designed For Use On Ferrous Metals, Plastic, Fiberglass, & Other Machinable Materials, Great For De-Burring, Sculpting & Removing Material In Hard To Reach Areas, Designed For Use With High Speed Die Grinders.