As seen on many different military rifles the M4 CQBR block 2 MK18 Mod 0 Mk12 all models. This helps keep gas and debris diverted from the shooters face and eyes. This features the rounded latch referred to as the “military Big Latch” extended to make it easier to charge the weapon especially with optics mounted or when wearing gloves.
I have used factory/standard charging handles before while running suppressed they do not vent gasses at all and it can get really annoying shooting with the gas in your face, it will even make your eyes water.
I have bought a PRI for all my rifles and love the fact there is little to no blow back in my face now. Definitely worth getting if you enjoy shooting suppressed.