Ball is diamond turned, after molding, to make it spherically perfect, which provides precise contact between ball and seats. Pipe Size 2 inch Opening Thru Ball 2 inch FKM (viton type) seals. Max PSI: 225 Polypropylene is reinforced with fiberglass for additional strength. Precision molded in polypropylene. PTFE self-lubricating stem bushings and seats cannot stick or bind. Self-aligning ball moves freely against the PTFE seats for smooth operation. Stainless steel bolts. Valve opens and closes with very little pressure on the handle. FKM: Advantages: Outstanding resistance to high heat; excellent resistance to oil, gasoline, hydraulic fluids and hydrocarbon solvents; good flame retardance; very good impermeability to gases and vapor; very good resistance to weather, oxygen, ozone, and sunlight. Limitations: Poor resistance to tear and cut growth;very little resistance to oxygenated solvents; fair adhesion to fabrics and metals. PTFE: Advantages: outstanding weather resistance, high resistance to ozone, and high resistance to the degrading effects of exposure to such solvents as acetone, MEK, and xylene. Limitations: Very poor elastic memory making it subject to tearing during installation.