This Nitrophyl float is resistant to modern ethanol based fuels and has a military spec closed cell construction making it puncture proof. The material used is simular to the material specified by the S.U Carburetter Company for military installations in the 1980s, where a guaranteed fail safe operation was critical. Will fit all MK1 - MK3 Spitfires equiped with SU Carburetors (2required)