25mm X 25mm    Fins spacing   Min. - 1.6mm   Max. - 4.2mm   zoom geometry Constructive specifications   Copper tube                     Ø 9,52 mm (3/8") Smooth-grooved   Fin Aluminium Prepainted aluminium Hydrophilic aluminium Copper Frame Galvanized steel Smooth / goffred / prepainted aluminium Peraluman Brass Stainless steel