The RMR style red dot sight can be switched on/off by pressing + button on the left side for 3 seconds. 5 levels of brightness are controlled manually by the same + button to increase brightness or – button on the left to decrease it. Originally designed for pistols, our version comes on a low clamp base to be mounted onto 20mm Picatinny rail. This is an airsoft replica of Trijicon RMR sight which is ideal for smaller short barrelled airsoft or air rifles of AKSU type