What materials is the Findenser made of? The outer metal body material that makes up the fins is Aluminium 6060. The material finish on the metal body is anodised BS1615. The internal glass body is made from Borosilicate 3.3 glass. The glass body is filled with de-ionised water. The end and inner caps are made from Acetal. The sealing material is high temperature silicone and FKM.