[WIDE APPLICATION] Suitable for various types of telescopes with outer diameter 84-115mm, including reflectors, refractors, Dobsonians, Mak Cas, and SCTs. [EASY MOUNTING] Easily mountable with 3 bolts for quick and efficient focusing, providing the best focus effect. [OPTIMAL FOCUS] Eliminates guesswork and visual challenges to deliver optimal focus quickly and easily. [THREE METAL POST MOUNTING DESIGN] Ensures the mask stays centered and prevents slipping during use. [LIGHTWEIGHT DESIGN] Aluminum alloy construction, 1mm thick and only 57g, ensures durability without upsetting the telescope's balance.