Tube-O discharge side fitting with an R-134a charge port. The fitting has a 3/4″-16 thread for the discharge (high side) line and a 1-14 thread on the Compressor fitting.
The fitting is made of steel, and uses O-rings for both connections. This fitting is common on York and Sanden Compressors. Please make sure the York you are mounting this to is not a Rota lock fitting. Rota lock fittings use white Teflon seals, refer to pictures to see the difference between a Rota lock and Tube-O fitting.