Acorn - Upside Down- Mens (Black) - Men's: The Upside Down is an ultra plush slipper that s sure to keep your feet warm. Durable rip-stop nylon uppers for durability. Insulated with goose down for maximum warmth. 14 degrees F comfort rated. Soft fleece lining wicks away moisture from your foot for optimal hygienic conditions. Knit cuffed collar. Non skid TPR outsole for maximum traction.