TS16949:2009, ISO9001:2000, DOT certificate Air brake coil with double layer nylon :• Material:PA,PU,double nylon ... plastic• O.D. of turn:110,90,80,70,60,50mm etc.• Helix turns/coil:12,16,18,20,22,24 ... (Polyurethane) TubeTubing -- PU (Polyurethane) air brake coils, spiral hoseDouble tube--Trailer air brake reinforced hose, air brake coil with double layerDouble tubing--Double ...