FOCUSER that most telescope users will ever need. Durable corrosion-proof plastic base and draw tube with eyepiece holder for 1.25”OD. Dual knurled focus knobs turns easily, ensures precise focusing, no back lash and has a 70mm focus travel. Fits on Newtonian reflectors for tube diameter 110mm, 140mm, 180, 200mm, 225 and 250mm at ease (Specify tube diameter at the time of ordering). It also makes a fine upgrade for an older STARTRACKER SYSTEM telescope. A worthy component for a home-built reflector / refractor too.