The Sensor DOUBLE FACE SET BEARS are made of a special knit and cut construction that allows for a reversible design. The side marked as "plus" has a surface made of micropolyester silk, so it is suitable as an inner side in warmer conditions. The side marked as "minus" is made of micropolyester staple, which makes it perfect for colder temperatures. The difference in thermal resistance between the two sides was laboratory-measured at 3.6°C.