Insulation materials for underground pipes and tanks including corrugated pipes engineered from high density virgin polyethylene (HDPE); corrugated plastic tubing and fittings therefor; insulating materials made of polyethylene foam; flexible pipes, tubes, and hoses, not of metal; flexible plastic pipe, not of metal; flexible plastic and silicone tubing used for transport of liquids for use in the field of drainage and stormwater; polyethylene pipe (-Term considered too vague by the Internati...