Check the listing for details. Seachem MatrixCarbon 500 mL / 17 fl. oz.. Condition: New. Listed at 17.99 USD. Seachem MatrixCarbon 500 mL / 17 fl. oz. Product #: SEA-103 MatrixCarbon" is a truly unique activated carbon. It is formed as a spherical bead for optimum hydrodynamics, and will not pack. It permits maximum water flow and contact with its high density of macroporous binding sites. MatrixCarbon" has a very low ash content as indicated by its minimal impact on pH. Even when added to distilled water, it does not raise pH above 7.0. While all carbons contain phosphate, regardless of false claims to the contrary, MatrixCarbon" has the lowest detectable leachable phosphate content of all major carbon brands tested. MatrixCarbon" outperforms other high grade carbons by at least two-fold when compared for total capacity to remove aquarium organic matter, rate of adsorption, and duration of use. Sizes: 100 mL 250 mL, 500 mL, 1 L, 2 L, 4 L, 20 L, 100 L Why It's Different Shape ---Spherical Mean Diameter ---2.39 mm Density ---0.49 g/cc Pore Volume (PV)--- 0.55-0.65 mL/cc Total Surface Area (TSA) ---500-600 m2/cc TSA/PV ---770-1100 m2/mL Iodine # --->1000 Molasses # --->600 pH in distilled water ---