TruGlo XR21 1x Red Dot - 3 MOA Red Dot - CNC-machined from aircraft-grade aluminum. Unlimited eye relief. Auto-off feature preserves battery life (4-minute idle from last button push). 3-MOA RED*DOT reticle for precise aiming 21 x 16mm multi-coated objective lens Ideal for mounting on RMSc optic-ready pistols Digital push-button brightness controls - 10 brightness settings Remembers last used brightness setting when powering on Motion-sensing "wake" feature 1-MOA windage and elevation adjust Waterproof (IPX7) design Picatinny rail mount included Battery included (CR1632 3V) 20,000+ hour battery life Lifetime limited warranty