The Valken RDA20 Mini Red Dot Sight is a low profile airsoft optic with a 20mm tube diameter. The RDA20 has a strong andlightweight nylon fiber reinforced housing, and mounts to most 20mm picatinny and weaver rails. This airsoft red dot includes a CR1620 battery to illuminate the bright single red dot reticle with 5 brightness settings. The red dot offers a phase coated lens for a clear image with true color, and the turret click value is 3 MOA field of view at 100 yards. They make a great first airsoft optic. We recommend our Valken Sight Protector Kit to help protect this red dot sight.