The built-in laser pointer is 1.2 cm in diameter. Without the top cover, it’s 6.6 cm long; with it on, it’s 7 cm long. It fits whether the cover is on or off. The outer sleeve has a groove, and the button needs to be placed in that groove. First put in the laser pointer, then tighten the nut, adjust its position, and use glue to secure the nut and the laser pointer together.