The FastFire 3 is the best selling red dot sight from Burris. 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.Features:Automatic brightness sensor adjusts brightness to match the environmental conditions, also has 3 manual brightness settingsBattery access is conveniently located on the top of the sight, automatic time out feature after 8 hr helps battery last up to 5 yearsThe 8 MOA dot is most popular for short range shooters, especially with handguns or shotguns, the larger dot makes target acquisition quickerUnlimited eye relief1 MOA click valueManual push-button and automatic brightness adjustment illumination control3 manual brightness levels, automatic setting reactive to environment illumination settings