1MM standard neoprene nylon out with THERMALSKIN in. THERMALSKIN is a type of neoprene surface finish used on the inside of the layering piece which adheres well to the skin improving the seal and reducing flushing. 1MM standard neoprene nylon out with THERMALSKIN in. THERMALSKIN is a type of neoprene surface finish used on the inside of the layering piece which adheres well to the skin improving the seal and reducing flushing.