If you work on HVAC systems, these FANOVO service access valves are an absolute must-have for your toolkit! This 20-pack gives you plenty of valves for multiple jobs or to have backups on hand. Each valve is made from thick, premium copper that's built to last through years of use without corroding or failing. The 1/4\ SAE x 1/4\ OD size with 4.7 inch length is the standard that works with most refrigerator and air conditioner systems. What these valves do is pretty clever - they let you remove or add refrigerant without having to completely discharge the whole system. You just mount them on the compressor outlet and you're good to go. They work with all the common refrigerants like R22, R410a, and R134a. The quality is seriously impressive - the copper is substantial, the threading is clean and precise, and they seal tightly every time. I've used these on both residential and commercial units and they perform exactly like valves that cost twice as much. Whether you're a professional HVAC technician or a skilled DIYer who knows your way around refrigeration systems, having a supply of these reliable access valves on hand will make your repair jobs so much smoother and more professional.