I purchased this last year at Ishii Sports. I've only used it once. Below is the description from NANGA: Down shoes to enhance comfort inside the tent. These cold-weather tent shoes combine NANGA's uniquely developed waterproof and breathable material, "AURORA-TEX®," with recycled down. These down shoes will keep your feet warm, and the shaft can be folded down for use as a short type. With excellent cold protection and waterproof breathability, they won't get wet from the cold air and water generated during outdoor activities and camping, providing comfort. ■Materials■ Outer fabric: AURORA-TEX Lining: 40dn nylon taffeta Insulation: STD white duck down 80-20% (650FP) Down fill: 60g ■Size■ ・Free size (22.0 - 29.0cm)