Emgee Kit-Kat Fuse are made from Pure materials including good quality porcelain & copper / brass parts. The ceramic is sand fine grain ceramic. The ceramic is non porus and has high electrical & mechanical strength. The current carrying copper & brass components are Pure and Robust capable of carrying their rated current. The copper strip is made from ETP (Electrolytic Tough Pitch) grade Copper. None of the components / parts are made of steel / iron.