Leader foam is a flexible, compressible, closed-cell polyethylene joint filler. Available in different densities and colors, in the form of sheets. It is a chemically noncrosslinked polyethene foam with closed cells, expanded 5 to 30 times. It has light and insulating properties. Water-repellent and highly-resistant to weathering and chemicals. The backing rod protects against penetration by gasoline and inorganic solutions. It is used as sealant and gasket material in various applications.