The Prier 370 Valve Parts are in a kit. The kit comes complete with the O-ring, and valve spring. It also has the brass screw. Which uses a flat head screw driver. The thumb screw, which works on the top of the valve, Is also in the kit. The o-ring goes in the valve. It works as a seal. The seat also goe inside the valve. The valve is also availabe in 1/2" and 3/4" inlets. All of the parts are Genuine Prier parts.