BOA-S Reviews feature the Wraith CO2 Stock by Wolverine Airsoft designed to allow users to use an HPA-powered airsoft rifle without the need to be tethered to an external air tank. In this case, this allows one to run an HPA engine with the CO2 cartridges installed in the stock... "I do an indepth review of the Wolverine Airsoft Wraith CO2 stock, with how it is, and the potential for a internal air setup."