Drive spindle extensions allow shanks of grinding and milling tools to be extended. They allow access to hard-to-reach areas and are clamped into the collet of the machine (air or electric grinder) or into the flexible shaft handpiece. Drive spindle extensions are a cost-effective alternative to special made-to-order burs and mounted points with long shanks. Extension for drive spindles with a working length of approx. 100 mm, a tool mounting of 1/4" and a shank holder of 3/8"." Recommended extension for drives with a maximum rotational speed of 20,000 RPM. 1 key DM SW 9/11 mm, 1 key STS D 3 mm and 1 collet 1/4".