Locating the housing for the batteries was a real pain in the a*s. In case this may help others, what you have to do is dissassemble the rail mount (careful, lots of tiny pieces you may lose!). Once you do that, you'll see a small cilindric cover holden by two tiny screws. Loosen up the screws, an you will find the batteries housing. Once you do that, the sight works like a charm. Like the real one, it doesn't have an on/off switch: will be always turned on as long as it detects ambient light (doesn't work in the dark). If you don't want the batteries to run empty, you only need to cover the lens with the provided rubber cap (or just leave it in a dark place), and it'll automatically turn off.
Locating the housing for the batteries was a real pain in the a*s. In case this may help others, what you have to do is dissassemble the rail mount (careful, lots of tiny pieces you may lose!). Once you do that, you'll see a small cilindric cover holden by two tiny screws. Loosen up the screws, an you will find the batteries housing. Once you do that, the sight works like a charm. Like the real one, it doesn't have an on/off switch: will be always turned on as long as it detects ambient light (doesn't work in the dark). If you don't want the batteries to run empty, you only need to cover the lens with the provided rubber cap (or just leave it in a dark place), and it'll automatically turn off.