The Ultra Violet(UV)-rays are emitted by the sun and are only in part absorbed by the Ozone layer which surrounds the Earth. The UV-rays are not only dangerous for the human beings’ health, but also for many materials which we use during our daily life, such as the Polypropylene and other plastic materials: if these one are not submitted to special protection treatments, they tend to discolour and to become fragile. In the LaMia chairs, Leyform , proposes, as a standard, UV-ray-proof Polypropylene, which is able to offset the UV-rays, thus creating an effective barrier and guaranteeing the mechanical durability and colour stability of all involved plastic materials.