The Novent Red A2L Locking Refrigerant Caps are code-compliant and prevent unauthorized access. Compatible with all refrigerants, including A2L, and feature 5/16" threads. Precision-machined from high-grade brass and covered by a shielding aluminum shroud. Novent caps require a special key for installation and removal. Proper installation helps stop accidental refrigerant mixing in A/C systems. Seals standard Schrader service valves on central A/C units and mini-splits to help prevent refrigerant leakage. Protects from severe injury or death resulting from the inhalation of dangerous gases.