Aluminium case is made of AA6063, the aluminium case is coated with eloxal wich is durable for 20 years. The epdm sealents are made according to DIN standarts 7863 and 7715 Couse the absorber is made of 11 piece rising tubes the efficeincy of the fins are about %95-98 that effects the totat collector efficeincy. Aluminium case is made of AA6063, the aluminium case is coated with eloxal wich is durable for 20 years. Keep in mind that only the best raw materials can be eloxal coated, If there is a scrap in the case material it can be only painted.