Astromania 1.25" High Precision Double Helical Focuser with 0.1mm scale for Telescope Lenses / Finder & Guidescope High Precision double helical focuser for guider scope / finder scope Interface. The solution for telescopes or telephoto lenses with sluggish focusing. The Focuser has a fixed orientation - so there is no rotation of mounted cameras or eyepieces - or also the field of view with your guide star - when focusing. Upgrade your R&P focuser by adding it to the end of the R&P focuser by using "Astromania M42X0.75 Female to M42X0.75 Female Thread Telescope Adapter - 9mm". Note: please make sure that there is M42X0.75 male thread on your R&P focuser. Item was made by Full metal, durable. The one side of double helical focuser is M31X0.5 male thread (including a M31X0.5 female thread to M42*0.75 male thread Adapter which you can change M31X0.5 male thread or M42X0.75 male thread on this side), there are 1.25" accessory collar with male T-thread flange (M42x0.75) and Accesory collar thumbscrews on the other side that you can install StarShoot AutoGuider or 1.25" eyepiece. Interface: 1.25 inch with M42*0.75 male thread, primary Mirror Interfaces: M31X0.5 Accuracy 0.1mm; Focusing stroke: 10mm; Minimum length: 46mm; Longest length: 56mm.