This product is a low density Polyethylene foam backing rod. It is closed cell and is CFC free. USAGE/PURPOSE ?? It is available in a range of diameters up to 50mm. ?? Excellent rebound recovery. ?? Excellent chemical resistance to most commercial chemicals. ?? Solvents and acids as well as oil and compatible with all sealants. LIMITATIONS Care must be taken to avoid puncturing when placing in joints. Use rounded tools.