Excellent quality M42 male thread to 2-inch adaptor with twist and lock compression ring for CCD cameras This is a very cool and nicely CNC machined adaptor with black anodised finish. It has a recessed external brass compression ring that expands inside a 2 inch focuser or other female 2 inch adaptor when the knurled thumb dial is turned. Both providing good centring of your camera and an amazingly very firm locking into position. - 2-inch (50.8mm) barrel - Threaded to take standard 2-inch (50.8 x 0.75mm) filters - M42 x 0.75 male camera adaptor thread - Compression ring (external self centre locking) - Pushback: 52mm - Weight: 170 gms