Advanced Armament Corp Ranger 5 RBP, Suppressor, 6MM, DMLS Haynes 282 Printed, High Temp Alphatek Finish, Black, No Mount Included, 1.375-24 Universal Mount Compatible, 1.5 Diameter 65018-BLK The Ranger 5 RBP (Reduced Back-Pressure) is AAC's first step into the gas mitigation market. With the Double-Helix Gas System designed in house for gas mitigation, AAC was able to reduce the majority of the gas coming back into the Shooter's face while not sacrificing sound and still providing AAC durability!