The therm a rest down coupler is a luxurious mattress topper that makes quick work of joining two therm a rest mats together and offers an exceptional level of comfort and insulation for a great night s sleep making it a must for your next trip with your partner the duck down fill makes this coupler incredibly lightweight and highly compressible while the polyester outer makes it feel like you are sleeping on cotton bed sheets this large sized topper is ideal for securely joining two mattresses