Down is a unique product of nature, and until today it still jcannot be beaten by synthetic fillings when it comes to packing volume and weight. The outstanding insulation qualities and amazing moisture contol gives you a wonderfully dry and warm sleeping climate. Because down loses its ability to insulate when it gets wet,, a down sleeping bag should always be hung up by the loop provided to dry out after sleeping in it This however does limit its use to drier climates.