The XPS3 sight is smaller than the former N-cell battery 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, magnifiers or Night Vision mount. Smaller, lighter and always fast; the XPS series is a great addition. This Holographic Weapon Sight is night vision compatible. This unit offers 20 Daylight Settings with an 10 additional for Gen I-III+ night vision devices.