Two small plastic mouldings which enable roll tubes to be connected to inexpensive white plastic pipe for construction of very large space frame structures. (The rings are heated in hot water and slipped over the piping, where they lock tight on cooling.) These rings open the possibility of full-scale space frames for exhibition systems, room dividers, etc. There are two types of ring - one with a single attachment hole and one with two attachment holes. Use 4mm dia. fastenings, such as plastic rivets . Each set contains 10 single hole rings and 10 double hole rings.