Diameter pipe size head is known as one of the chemical fittings for connection of two different diameters. Head size is divided into concentric and eccentric head. Diameter pipe diameter pipe materials including stainless steel, alloy steel, carbon steel size head diameter pipe diameter pipe 20 steel q234q345 like. Product Standard GB American Standard British standard and non-standard high-pressure stamping "steel plate pipe fittings" quality provisions GB / T13401-2005 of Reducer Standard reducer should be consistent with current national standard "welded steel seamless pipe fittings "GB / T 12459-2005 standard GD0506 ~ 0507 Ministry of National Standard (GB / T9112-2000) machinery of the standard (JB81-59, JB / T74-94) OGC standards (SH3406-96) Ministry of Chemical Industry Standard (HG5010- 58, HG20592-97)