QAN1016 Features: * Crushed coral * With aragonite, provides more buffering power * Dolmite or oyster shell * Use in under gravel filtered systems or reverse flow beds * Solid and economical performer * Grain size 2.0 - 5.55 mm Dimensions: * Weight: 15 lbs * Dimensions: 2.5"" H x 12"" W x 19"" D