GDU type ① d hot zone diameter I hot zone length m cold end length E central distance n Al-sprayed length L overall length Product marking: GDU type: 2 x d / I / m / E GDU type ② d hot zone diameter I hot zone length m cold end length E centre distance D outside diameter of connecting part K the width of connecting part n Al - spayed length L total length product marking : GDU type : 2 x d/I/m/E - K