The Novent Pink R-410A Caps are precision machined from high grade brass & covered by shielding aluminum shroud, & special tools are needed to apply/remove Novent caps. All caps are embossed & color-coded. Proper installation helps stop accidental refrigerant mixing in A/C systems. Seals standard Schrader service valves on all central A/C units and mini-splits to help prevent refrigerant leakage, Protects from serious injury or death resulting from the inhalation of dangerous gases.