... 2000, DOT certificate Double layer nylon tube reinforced tube :1).Material: PA, Nylon ,Polyamide2).Size: O.D.× ... -- PA (Polyamide, Nylon) Coil TubeTubing -- PA (Polyamide, Nylon) TubeTube-- PU (Polyurethane) TubeTubing -- PU (Polyurethane) air brake ... coilsDouble tube--Trailer air brake reinforced hose, air brake coil with double layerDouble tubing--Double layer nylon ...