【Aluminium Alloy Material】 Made of high strength Aluminum with Anodizing Aluminium Process. Precision machined solid aluminum finder shoe base in matte black, for almost all viewfinder holders, for the "Witty 1" Tangent-attachment etc, fits all lens barrel radii. | 【Easy to Install】 Two large knurled thumbscrews makes it easy to install: Bases feature two large thumbscrew locks to secure your finder scope or reflex sight in place, even while wearing gloves. Just put it on the optical tube and tighten the screws. | 【Multi-Function】 There are two elongated holes on this base and a single countersunk hole for screws up to M5 in the middle. Two screws are on the side of base. The distance between the center points of the screw holes is 24 to 41 mm | 【Well-Engineered in Shape】 The base forms two linear constraints on each tube radius of 130-400mm in diameter, which gives maximum stability. The base also carries small guidance/CCD guider without any problem. | 【Practical Funcationality】 Synta-style dovetail base -- Fit most bracket designs from Celestron, Orion, Sky-watcher, Vixen, etc. Compliable with finder scope, Laser Pointer bracket on telescopes.