PCO-S Solar Pistol Optic: The Pistol Combat Optic-Solar or PCO-S is everything you love about the PCO, plus solar back up. With the exception of the silhouette and the solar cell, which extends your battery life up to 50,000 hours on a single 1632 battery, the PCO-S is identical to the PCO. It has the same 3 MOA dot, RMR footprint, co-witness channel, and top load battery. The same 1632 battery, four minute , and shake awake feature. The biggest difference is the extended battery life and the more angular shape of the arch. We love the PCO-S and you will too. Do yourself a favor and give your pistol the upgrade it deserves, give it a PCO-S.