Waterproof and Shockproof Reflex Mini Red-Dot Sight, XT3 Very compact open sight XT3 may disappear out of sight in a hand. Because its overall sizes are 45 x 27 x 27 mm (LxWxH) and its weight is only 33 gr. The brightness of the red dot can be controlled automatically by a photo cell disposed at the front of the sight, corresponding to ambience. The XT3 being in a rugged aluminum monocoque structure withstands heavy impact. Accurate adjustment of elevation and windage can be done, feeling and hearing a “click”. Easy battery insertion and changing. A CR2032 battery can be insert to a battery compartment disposed at the right side of the sight. Changing of batteries is available without dismounting the sight from the firearms.