Maxim Defense's Roller Delayed Buffer (RDB) System transforms your 9mm AR-pattern firearm into a roller-delayed blowback system, reducing felt recoil and boosting reliability.By allowing gas pressure to stabilize before extraction, it ensures smoother operation while virtually eliminating friction common in standard buffer systems. FeaturesReduces felt recoilincreases reliabilityMinimizes friction for enhanced performance Notes:The RDB System is designed specifically for 9mm AR platforms and is not compatible with other calibers.To install the Roller Delayed Blowback (RDB) System, your 9mm bolt assembly must have an open channel to allow the guide rod to function properly during firing. For most 9mm bolts, meaning you will need to remove the pinned-in central mass. The central mass must be removable, but the bolt carrier group (BCG) should retain its full length without it, to ensure proper function with the RDB system.