These provide extra travel (focus length) needed for some telescope/eyepiece combinations. Made of anodized aluminum with a brass clamping ring. Has locking screws and the brass clamping ring is to ensure a secure fit. The extender tube is 2" long and the attached barrel is an additional 1-3/16" long and threaded for filters. New/Unused. We have seen these selling online for as much as $65.00. Wollensak Optical, quality optics since 1899
