Flexible Ducting Hose Structure Our Duct hose has a specially compounded rigid PVC reinforcement which is helically wound and inseparably fused to the soft inner walls. By its unique construction, ducting results in a thin, very smooth wall, being almost completely protected from any possible crushing. Tube: Synthetic Rubber –Black Reinforcement: One Braid of High tenacity yarn Cover: Synthetic Rubber-Blue & Red Working Temperature: From -30 °C to +70 °C continuous operation