The Holosun HS515CM is a micro red dot optic. Switch from a 2 MOA dot to a 65 MOA circle dot with a push of a button. Holosun's highly efficient light emitting diodes and solar panels allow Holosun solar optics to run without a battery in many lighting conditions. Additionally, the back-up battery lasts up to 5-years on the dot and up to 2 years on the circle dot. The U signifies a housing design that shrouds the windage and elevation turrets on two sides. This product includes clear flip-up lens covers, a quick release mount and a kill flash filter. Parallax free with unlimited eye relief LED technology allows up to 50,000 hours of operation on one CR2032 battery 2 MOA dot and a 65 MOA ring Parallax-free with unlimited eye relief Powered by both battery and solar Quick Detach 2 piece mount included