Caribbean Crushed Coral - The classic ""crushed coral"" is now available in colorful 20 and 40 lb bags, Helps maintain pH, Good sphericity and high uniformity coefficient combine resulting in excellent flow rates, Use in traditional undergravel filtered systems or reverse flow beds, The price is right, too! Grain size 3, 0 - 6, 0 mm, 20 lbs, SKU: RYLHC1140