Used inside the nitrous is a collection of 3d, vertical v-baffles filled with 800+ loft dwr down; a full zip allows venting while the box foot prevents cold spots; and theres a draft tube, three-quarter hood and internal chest drawcord. The nitrous is also versatile. Other features include vapour vent fabric with a water-repellent coating and a zip protector on the ykk zip. 800+ loft dwr-treated duck down is our premium choice a must for the gram counters. This high-lofting white duck down delivers luxurious warmth at a fine, feathery weight. This down has excellent compactability and loft recovery. Down is the best insulation for lightweight sleeping bags due to its loft, compressibility and durability. However, this golden fibre has a failing: its ability to insulate drastically decreases when it is wet. Nitrous sleeping bags are made using lightweight and highly breathable 15-denier vapour vent fabric. This strong, compressible and highly breathable fabric is downproof by construction: the tight weave keeps the down in but allows water vapour to escape. This reduces the possibility of clamminess and allows the down to loft fully for maximum performance.