The Rosco Non-Adjustable Gas Blocks are purposely designed to be lined up perfectly with their barrels and gas ports to ensure reliable cycling every time. Rosco has created two options for the end user; their Non-Adjustable gas block is a direct plug in for any one of our barrels and has provisions for pinning. Rosco Manufacturing's "Bloodline" series is their hardest working category. Whether you are an occasional builder, tactical shooter, or Law Enforcement Officer they have a product that will fit your needs. All Rosco's Bloodline accessories are designed to take the abuse from unconventional wear and tear that their customer may need to inflict on their Mfg: Rosco Manufacturing