These containment systems are used every day in industries where it is undesirable to get contaminants spilled on the ground or worse into the water shed from pipelines, engines, or even stored chemicals. These foam filled units can be driven over without damage. The foam just expands back into shape. They are light enough to be portable. They can be made in a wide range of sizes and colors. The foam inside is polyurethane foam rubber, the bottom is 42 oz pvc coated polyester, and the ring is 18 oz pvc coated polyester truck tarp material.