Like a puffer jacket for your feet. the Thermoball Traction Mule from The North Face features a quilted ripstop nylon upper woven entirely from recycled materials and packed with proprietary ThermoBall eco insulation. A pull-tab rounds the collapsible heel while half dome logo embroidery lands atop the forefoot. Layered underfoot we find a rubber midsole set atop a treaded rubber outsole for traction.