HDPE double-wall corrugated pipe is made of high-density polyethylene by extrusion molding, showing a double-layer structure with smooth inner wall and corrugated outer wall. Its core performance is measured by ring stiffness, commonly SN4, SN8 grade, can withstand external pressure of 4000Nm², 8000Nm², suitable for buried depth of 2-5 meters of drainage, sewage scenarios.br Welcome to contact us:br Whatsapp: +852 67433414br Email:samwang601@gmail.