TS16949:2009, ISO9001:2000, DOT certificate Air brake coil with double layer nylon :• Material:PA,PU,double ... M16,M18 ,M22 ,1/2"fittings etc. or no fitting• Type:European style, American style, ordinary type ... -- PU (Polyurethane) air brake coils, spiral hoseDouble tube--Trailer air brake reinforced hose, air brake coil with double layerDouble tubing--Double layer ...