Crocs Classic Convertible Slipper Slippers Unisex Black / Black M11. Comfy And CuddlyCuddle up on cold days with this comfy slipper that features a convertible heel for easy on and off wear. Even better, it has a durable polyurethane outsole for additional traction indoors and out. With warm felt construction that comes in a range of neutral color options, you can slip into blankety softness all winter long. Classic Convertible Slipper Details: Soft and warm footbed Polyurethane outsole for additional traction