As standard our bases have the U-value of 0,78! But we can produce them with even lower U-values , let us know what you need. And for the lids the U-value depends on what kind of material and how thick polycarbonate or how many layers of domes. So just let us know what U-value you need. Here comes our article numbers that can be specified on projects. Firstly our opening system with gas-springs ,fusible link + electrical magnet: This is with 300mm high standard base and covered aluminium lid: B1010-30-1-1-10. Then same base with multi-walled polycarbonate as lid. : B1010-30-30-1-10. if you want dome as lid instead of multi-walled polycarbonate , then just ad "with dome" , and how many layers. And when you want a 500mm high base you only change the numbers to: B1010-50-1-1-10 (covered alu-lid). And B1010-50-30-1-10 (daylight lid). And for our special renovation base you just have the numbers: B1010-3R-1-1-10 (covered alu-lid) , or B1010-3R-30-1-10 (daylight lid). And when you want an opening system with electric motor you only write the number 31 at the end , instead of 10. (example B1010-3R-30-1-31). All the B1010 have one lid.