High fired, Alumina body. An excellent material, extremely porous, and inert to most all solutions. Hard exterior and interior surfaces and pure white in color. Recommended for low air pressure differentials not exceeding 0.5 Bar (7.25 psi). Typical bubbling pressure: 12-16 psi. Effective pore size: 6.0 microns. Hydraulic conductivity: .0000311 cm/sec. Approximate porosity: 50% by vol. Typical flow through for a 1/4-inch plate: 180 ml/hr/cm2 at 14.7 psi. Ideal for liquid or gas sampling as the Alumina material has almost no ionic exchange sites or leachable mineralogy. Truly a superior ceramic for both industrial and scientific work where high volume transfer or testing at low pressure differentials is needed. All cups are "as cast".