This is a # 8 90 Degree Female Oring Fitting with high side port. It will screw onto a Sanden oring compressor discharge fitting. It includes a switch port with a binary switch and pigtail. The purpose of the binary switch is to turn the compressor clutch off when the refrigerant pressure gets too high, to prevent damage to components and catastrophic failure. The binary switch will also keep the compressor from coming on when the pressure is too low, like when the outside temperature is too cold, or if the system has lost its charge.