Foredom Duplex Spring Handpiece Great for Flex Shafts. This is a new Foredom #10D duplex spring handpiece. Includes a rapid release lever for quick tool changes. Has a duplex spring for maneuverability and flexibility. Has a slim diameter hand piece with a knurled grip. It runs cool for prolonged periods at low speeds and has pre-lubricated ball bearings. For use with 3/32" (2.35 mm) shanks.