These locking caps are designed to provide superior protection for your A/C unit's refrigerant system. Made from high-quality materials, including precision-machined brass and aluminum shrouds, they screw on tightly to seal standard Schrader service valves on virtually any A/C unit and mini split. The 1/4" size ensures a secure fit and prevents leakage or misuse of refrigerant. By reducing venting and energy loss, these locking caps can help you save money on utility bills and prolong the life of your A/C unit. With their durable construction and reliable performance, they are an essential investment for any homeowner or business owner with an A/C system.