One inch 1/4 threaded hole and two M5 threaded holes are added, which not only increases the connection with the telescope body, but also enhances the stability of the connection, making it possible to connect more external accessories. Specification This base fits under all red dot finders with 21 mm mount. It allows fixing the finder to the telescope solidly Suitable for Starpointer LED Finder scope from Skywatcher, Celestron, Orion, Baader SkySurfer and similar systems Accepts all sights designed to fit a standard Picatinny rail;Fits into standard finder shoes by Skywatcher;GSO;Celestron;Vixen;Orion Fits the dovetail mounting base on most telescopes All metal construction and anodizing aluminium process, durable for long time use Great for both visual observers and astrophotographers Attach finder scopes or other aiming devices to your telescope quickly and easily (by Dovetail Clamp).Use of aiming devices you wish including finder scope, red-dot reflex sights, green laser pointer brackets, mini guide scopes, and more. All-metal construction, Made from black Anodized solid Aluminum. It will be stronger and more durable. It will not be easily damaged and will stay with you for a long time. Dovetail slots can be installed for SKYRVER 80ED, 102ED, 130APO; SKYRVER 100ED binoculars; and other primary mirror; also Fits for all Sky- watcher telescope and Vixen telescopes. Main advantages: Universal dovetail base for finder scope: Ideal for custom installation of a finder scope on telescopes not already equipped with a compatible base Please note: There are no attachment screws to hold it to your optical tube assembly; it is suitable for M4 threads screws to assemble for your optical tube;and easy to use and just put it on the optical tube and tighten the screws. High strength aluminum with anodizing treatment CNC machining ensures smooth surface and precise cutting of rail, it fits your telescope perfect Made of premium aluminium alloy, solid construction is wearable and