TOOLS 4X Upper Buffer consist with 0.5M Tris (pH 6.8) and 0.4% SDS at the optimal concentration for convenient and quick preparation of polyacrylamide gels for protein analysis by SDS-PAGE. Dilution of 4X buffer to a 1X solution (0.125M Tris and 0.1% SDS) can be used in the preparation of the stacking gel for SDS-PAGE.