The HS403R is a small compact micro red dot optic that features Holosuns new rheostat dial to adjust brightness settings. The HS403R can achieve a constant "on" battery life of up to 100,000 hours! It has a 2 MOA dot size, unlimited eye relief, unlimited field of view, and has a IP67 waterproof rating. A low mount and 1/3 Co-witness mount is included.