17 Plastic trunking and ducting; plastic connectors; plastic conduits; plastics in the form of sheets, strips, blocks, rods, tubes, and shaped sections for general industrial use; flexible plastic tubes for use in plumbing; flexible plastic tubes for use in supplying and distributing gas; plastic pipes for use in plumbing; plastic pipes for use in supplying and distributing gas; non-metallic pipe collars; non-metallic pipe couplings; non-metallic brackets for supporting pipes; pipe end fittings; and parts and fittings for all the aforesaid goods