Made by the respected Clarence Lai with RedWolf Airsoft... "This Red Dot fits all 20mm rails, and is powered by 1x CR2032 Lithium Battery. The tubeless design reflex lens aperture provides a wider field of view compared to traditional tube reflex sights, making this Tactical Sight perfect for rapid firing or shooting at moving targets besides normal target shooting.

The red dot is firmly factory adjusted parallax-free to 40 yards. This adjustment ensures the parallax-related errors are minimized over long distances. The red dot position is fully adjustable in both lateral and vertical directions. Package also includes screwdriver, cleaning cloth, lens cover, hex key and 1x CR2032 battery."