Vermiculite Grade C - 3 is a medium particle size material meeting ASTM C516 Type 1, Grade 3 specifications. The material is widely used as a component in growing media for professional growers. The swimming pool industry uses large quantities of this material mixed with Portland cement to make a lightweight concrete underlayment for vinyl pool liners.The unique properties of vermiculite insulation and cushioning lengthens liner life and performance. Packaging : 18-22 lb. kraft bags: 30 Bags/Pallet Bag Volume: Approx. 4 cf