Consists of a flexible silicone, does not cause particular gene. In less than three days, it is perfectly used and the product becomes even essential as it improves the quality of sleep. For those who have a deformity of the nasal septum like me with diameters of different nostrils, it is possible to insert a tube into another larger diameter tube and have two different diameters at the ends. The tubes are well adjusted to each other, the improvised assembly holds well. We must sink enough tubes in their nostrils so they do not untap during the night. The tubes are very flexible, you soon get used to it. Easy to maintain and durable. The simplest solutions are often the best!