One side of the post holder thread adapters is screw, the other end is hole with inner φ 6 mm and depth of 5.6 mm. There are 2 types of 4-40 screws and M3 screws, compatible with components with internal 4-40 or M3 threads, suitable for connecting Φ6 mm cage post. M3 set screws are attached on the side for fixing Φ6 mm cage posts and Ø1.8 mm through-holes on side, compatible with 1.5 mm wrench for reinforcement connection. The thread adapters effectively realizes the series connection of the components in the cage system.