Smart Pots 12120 Compost Sak Fabric Composting Container High Caliper Compost Sac By the makers of the Smart Pots, the Compost Sac is constructed from a textile fabric that is lightweight yet extremely durable and will last for years This rugged fabric is extremely porous containing an enormous amount of micro-pores that allow for constant air circulation and excess water to drain Aeration and water (but not too much) are two of the key components to successful composting