Seals standard schrader service valves on all central air conditioner units and mini-splits to help prevent refrigerant leakage. Protects from serious injury or death resulting from the inhalation of dangerous gases. Refrigerant caps are embossed and color coded for easy use. Proper installation helps stop accidental refrigerant mixing in air conditioner systems. Refrigerant caps resist crushing and removal without cap key. Corrosion and resistant anodized aluminum. Refrigerant cap tool is needed to remove caps. Pink cap 5/16" thread 2 pack; precision machine made from high grade brass and covered by shielding aluminum shroud. Great home improvement, anti-theft, and safety product. O-ring resists oil and sealants. FOR THE TRADESMAN: RectorSeal is recognized as a leading provider of quality solutions for the professional trades serving heating, ventilation, and air conditioning (HVAC/R), plumbing, electrical, and construction markets.