The Holosun HS515CM is a micro red dot optic. The operator can 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. 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. Parallax free with unlimited eye relief.New advanced technology LED allows up to 50,000 hours of operation on one CR2032 battery2 MOA dot and a 65 MOA ringParallax-free with unlimited eye reliefPowered by both battery and solarIncludes Flip-up lens covers and Kill FlashQuick Detach 2 piece mount included