Stant's Lev-R-Vent series radiator cap are standard SAE ñAî size,  and does include upper gasket so they are for use on open and closed cooling systems.

Features

    -The Lev-R-Vent» features a patented lever release to safely release pressure for quicker cooling.
    -Meets Original Equipment specifications.
    -Made from premium materials.
    -Designed to function on open cooling systems and overflow reservoir type systems.