A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section with diameter from 16 to 1600 mm, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders, masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members. The pipes can be produced from PP, PE, ABS, PRX, PEX and some other material.