12" X 52" NSF Certified polyglass tank with base, lifetime warranty. Pentair/Fleck 7000 Digital Control Valve, 5 Year control valve warranty.Calcite media used to balance pH levels to 71/8" X 1/16" Coarse gravel.Calcite media is used to neutralize pH levels that are acidic (pH levels less than 7). Calcite is calcium carbonate which automatically self-limits the dissolve and stops at a pH level of 7.