FastFire 3 is the best selling red dot sight from Burris. It is available with a 3 MOA or 8 MOA dot. Light and tough, the FastFire 3 series puts an unmistakable, bright red dot on your target to give you an immediate speed and accuracy advantage. Can be used as a primary sight or paired on top of an existing sight. Automatic brightness sensor adjusts brightness to match the environmental conditions; also has 3 manual brightness settings. Battery access is conveniently located on the top of the sight; automatic time-out feature after 8 hours helps battery last up to 5 years. Available with Picatinny/Weaver mount for mounting on guns. FastFire 3 red dot sight features: Bright red dot allows for fast target acquisition and easy aiming; Compact and lightweight, so it won't affect firearm balance or handling; 1x magnification allows both-eyes-open shooting, for enhanced awareness and target acquisition; Parallax-free, for better accuracy; Mounts to almost anything using Burris mounting systems; Automatic brightness sensor adjusts brightness to match the environmental conditions; also features 3 manual brightness settings; Windage and elevation adjustments make optic fine-tuning easy; no special tool required; High-grade optical glass provides excellent brightness and clarity