From Mr. HVAC

This tool kit is a must have. It is used to remove the small core (valve) that refrigerant gauges connect and controls to. These valves often leak and should be replaced as part of any thorough annual precision tune-up. Missing caps should be replaced too and they are included in this kit. This is a complete kit that includes a high quality tool, R410 brass adapter, 20 valve cores, and 10 brass valve caps. This kit would be used for most any residential and commercial HVAC or refrigeration system.

This kit is the best combination of solid build quality and price that I could find. This would make a great gift for a service or installation technician.

Adapted from Amazon

• Dual Size SAE 1/4 & 5/16 Port, R410 R32 Brass Adapter, 20pcs Valve Cores and 10pcs Brass Nuts
• Made of solid brass, durable, able to be opened and closed in quickly and conveniently.
• External bypass port design, which can remove the valve cores.
• The metal knob is all anti-slip design.