NOVENT® locking caps seal standard Schraeder service valves on all central AC units and minisplits to help prevent refrigerant leakage. Novent provides dual protection with a single screw-on installation. Safe guard your AC system's efficiency and the environment from lost or accidental mixing of refrigerant gases. Help protect children from serious injury or death resulting from the inhalation of dangerous refrigerants. Patented Novent Caps are precision machined from high grade brass surrounded by a protective aluminum shroud and can only be installed and removed with a special tool.