The 403B is a small compact micro red dot optic. Employing Holosun's LED technology, the lifetime for one CR2032 battery can be up to 5 years. This optic features Holosun's Shake Awake technology that powers the optic on with slight movement of the 403B. It may be installed on various firearms such as shotguns, pistols, air rifles and crossbows. The HS403B is compatible with standard mounts.