A very high molecular weight polymer, used as Processing Aid in foamed PVC formulation. Its tailored molecular weight distribution helps to better control and optimize the melt flow of the foamed PVC formulation through wide dies for free foaming extrusion process. SURECEL™ 4280 Processing Aid stabilizes the formed structure to lead to foamed PVC sheets with high cell density and small cell size. The thickness of the final product is well controlled, and a low density can be reached without damaging the surface roughness.