The Flux Raider SBR +1.5 and +3 stocks comes with 1 stock compatible gas cap. The Flush SBR stock does not come with a gas cap. The brace gas caps are not compatible with the +1.5 and +3 stocks. The brace gas caps are compatible with the Flush stock.
Installation video found here:
If you are having trouble installing your stock, we offer an install service: