The XPS3 sight is smaller than the former N-cell batter sight (511/551). It runs on a single CR123 battery and it has a longer battery life than the N-cell style sights. With the single battery configuration, the XPS allows more rail space than ever, leaving more room for rear iron sights or NV mount. Smaller, lighter and always fast; the XPS series is a great addition. This unit offers 2 X 1 MOA Dots in the reticle surrounded by the 68 MOA ring. This unit offers 20 Daylight Settings with 10 additional for Gen I-III+ night vision devices. Features Auto Shut Down at 8 hours.