The Holosun 507 Comp Green is a competition style green dot sight with an RMR footprint and a very large window. It’s designed to compete against optics like the Trijicon SRO, Vortex Defender XL, and Leupold Delta Point Pro. It’s intended for use on compact or full size pistols and will fit any RMR cut slide or adapter plate. The extra large window makes it very easy to find the dot and to acquire targets making it perfect for competitive shooters. An innovative feature of the 507 Comp is its reticle system named the Competition Reticle System (CRS for short). The CRS Reticle gives you a total of 8 reticle configurations. There is a 2 MOA center dot, 8 MOA outer ring, 20 MOA outer ring, and 32 MOA outer ring. By holding down the “-” button for 3 seconds you can cycle through each of these ring + dot combinations to see which suits you best. We found the 32 MOA outer ring + 2 MOA center dot to be pretty nice. In addition to its large window, the 507 Comp features manual brightness modes, side removable battery, IP67 waterproof rating, 20K to 50K hours of battery depending on brightness and reticle, and has a strong 7075 T6 Aluminum housing. If you are looking for one of the largest window pistol red dots on the market, this is it. This optic has a green reticle. Green has a few benefits: Green reticles are less straining for the eye to see. Green reticles can help with astigmatism. If you have astigmatism you will see a blurry dot, we have been told by a few customers that Green dots help with their astigmatism, making the dot look more crisp than the red version. Green will not washout on backdrops like green grass, foliage, or green colors. In theory Green dots can have a longer battery life because Green is brighter, so for example a green dot on brightness setting 6 may be the same brightness as a red dot on setting 7 - which would save battery life. If you want to learn more check out our full article about Red vs Green Dot Pros & Cons here.