14,000 strokes per minute. .007in stroke length (.018 mm). precision removal resulting in less risk of gouging delicate parts. less aggressive than a Die Grinder. Lightweight and Faster than hand-filing. Only one wrench required. easier to change files. Easy grip rubber sleeve. Includes 1/8in collet insert. Accepts 1/16in , 3/32in , 3 mm collet inserts (sold separately).