Wide range of applications. Suitable for all types of telescopes, mirrors, refractors, for Dobsonian telescopes All you need to do is measure the size of your telescope tube and choose the right mask size. The mask takes the guesswork out of focusing and even overcomes vision conditions to get the best focus on your telescope quickly and easily. 3 metal posts. The mask gently and firmly grips the telescope tube with three metal posts. These metal posts are fitted with scratch-resistant silicone covers to protect the surface of your telescope. This prevents slippage while keeping the mask perfectly centred. Post mounting and lightweight design. Thanks to this 3-post mount, the mask stays centred while fitting a wider range of telescope Suitable for sizes. telescope objectives in the 100-140mm range (1-2mm error in manual measurement). Colour: Original wood colour Size: 90mm Product list: Fishbone plate*1 piece Screws*3 pairs Screws anti-slip sleeve*3pcs