The BSA Multi-Purpose sighting systems are a wonderful lightweight sight for close quarter and medium range targets. Light enough for small calibers, plinking on the range, yet durable enough for larger calibers used by hunters and law enforcement departments. The 5/8-3/8 adjustable mounting system is perfect for shotguns, rifles, pistols, bows and crossbows. You can adjust the brightness of the dot, depending on the brightness of your surroundings NOTE: 1) Move the sight back and forth until the correct eye relief distance is achieved 2)If the dot appears to have a halo or be out of focus the brightness setting should be reduced until it is clear and sharp..