Hex Key Adapter, Size 3/16 In. and 5/16 In., Steel Material, 5-3/4 In. Length, Opening and Closing Most Base Mounted Service Valves on A/C Units This hex key adapter is designed for opening and closing most base-mounted service valves on AC units.
Very impressed with they way they are built. Been using cheap ones for years.
Thought I would treat myself and upgrade. Highly recommend these types of gauges.