Most UK suppliers of use polycarbonate or glass for their domes or inlet points. Polycarbonate is in-expensive, easy to mould and very strong, unfortunately it tends to go yellow and cloudy when exposed to UV. Glass will always maintain a reasonably clarity but needs to be quite think to have the necessary strength. Solarspot systems use Acrylic (PMMA) for their domes. Whilst Acrylic delivers all of the required tensile requirements for this sort of application and allows for consistent manufacturing reliability, it possesses much better UV resistance. Acrylic is also optically superior to glass and has no visible colour tint.