Glycerine is the standard fill fluid and provides the best performance in most applications. Silicone has a low viscosity and works well when extreme temperature fluctuation or icing is expected Features: 1) Size: 1.5", 2", 2.5", 3.5", and 4" available 2) Pressure range: 15 to 15,000psi 3) Vacuum, and compound available Inner packing: 1pc/box Outer packing: 25, 50 or 100pcs/carton ;