Melonited gas plug assembly for use with our kits, uppers, or rifles. For use ONLY with Standard Picatinny Gas Blocks with Adams Arms Piston SF-308 platforms (.308 WIN or 6.5 Creedmoor). Do not install for 5.56 (5.56 gas plug available at this link: Standard Gas Plug 5.56). Gas block sold separately. This is a spare or replacement part for Adams Arms only.