Open Reflex Red Green Dot Sight with 4 Pattern Ractical with Weaver Picatinny Rail Mount Rails Unlimited eye relief and red and green dot and built-in pica tinny mount base for easy sight remounting. Black anodized aluminum construction and 100% safe for eyes. Objective aperture is 33mm, field of view (@ 100yds) 15.8m@100m, length is-82mm and rail size is 22mm. Water proof, shock proof, and complete with integral picatinny mounting deck with double locking nuts and flip-open lens caps. On and off switch red and green dot sight adjustable reticule brightness.