Cultivation Tools Click to enlarge image(s) 3lbs. pH buffer widely used by cultivators who use spawning substrates or casing soils. Oyster shells are a great source of Calcium Carbonate, as well as help provide support for bigger fruit bodies in casings. Oyster Shells are crushed to size, and are clean. SKU CRUSHED_OYSTER_SHELLS Weight 3.0 lb 3 lb bag OR 10 lb bag 3 LB. BAG ($0.00) 10 LB. BAG ($12.65) Price $3.00 Qty Add to Cart Submit a Review... Rating 5 4 3 2 1 0 Title Review Name Email For security purposes, we ask that you enter the security code that is shown in the graphic. Please enter the code exactly as it is shown in the graphic. Enter Code Submit