The client is free to choose between SSt and Copper ferrules. Most our clients choose SSt ferrules as they are made of the same 316 grade SSt as the wire and HELIMESH 25 tube frame. Only difference is the higher content of molybdenum 2.5 instead of 2.0 percent. Copper ferrules doesn’t corrote althoug made of dissimilar metal to stainless steel. The reason is that Copper has the ability to protect itself with a thin layer of Copper oxide.