Heat Backpacks & Travels Black"Heat" Porter Yoshida & Co one shoulder backpack "Heat," made of 66 strand woven varistor nylon, a high strength material used for airbags and body armor. The structure is supported by high density nylon tape at key points, which maintains the three dimensional silhouette. Parts of the surface are made of waterproof tarpaulin fabric for industrial use, with contrasts given by the combination of different materials and textures. Military inspired