The Crescent Lake series sleeping bags are made with Techloft+ insulation. Techloft+ Insulation consists of multi-hole staple-length micro-denier fibers that have a siliconized finish for maximum insulation loft and compactness. The Crescent Lake uses a 2-layer offset construction sometimes called a bag within a bag. The contoured hood and mummy shape helps seal up your warmth and keep you warmer.