Ideal for gravity surface water and storm water drainage applications such as highway filter and carrier drains, rail track drainage, golf course land drainage and much more. Made from HDPE plastic manufactured by twin extrusion process in which two layers are simultaneously extruded one inside the other, heat welded together. The outer wall is corrugated providing excellent strength, Reducing the possibility of on-site damage. The inner wall has a smooth seamless finish to assist hydraulic flow. This design prevents silt accumulation.