Install these magazine lip gas seals to make your ProWin magazines compatible for the Inokatsu M4 Gas Blowback series. This package includes 5 custom gas lip seals. But before you use these magazines in an Inokatsu M4, make sure you install the stiffer hammer spring in there first. The reason is that the Inokatsu M4's hammer spring is a bit too soft to strike open the valve on ProWin gas magazines. So if you haven't already installed a stiff hammer spring, get the >u>ProWin Magazine Lip Gas Seal and Hammer Spring for Inokatsu (Pack of 5) first. You can find it below in the RELATED PRODUCTS section. Once you've installed the stiffer hammer spring, you can come back to buy this set of 5 lip seals for additional magazines.