The unique manufacture of Five Star polytunnels allows for further tensioning of the polythene after completion of covering and provides a method of concreting the ground tubes in without needing to worry about their height. Unlike some manufacturers, Five Star polytunnels provides an exhaust clamp which is fitted to the ground tubes after the ground tubes are set. These clamps can be fitted to a string line to ensure correct levels. The hoop is then fitted over the ground tube to rest on the clamp. This set up allows the whole hoop to be lifted inside the polythene and the clip to be raised as a final tensioning facility. This ensures the polythene is extremely taut, which will extend the life of the polythene.