This Highlander echo 400 sleeping bag is ideal for extremly cold conditions. The bag is designed to keep you warm from head to toe. The foot box and 3D neck baffle provide you with extra protection and comfort. Other features include 8 to -9 degree C comfort range, -27 degree C extreme temperature, soft polyester 240T microfibre inner filling and cire W/R coated polyester ripstop 210T outer filling. QFX3D fabric is a specialist fibre filling that has been designed for use in outdoor applications such as sleeping bags and quilted outer garments. The best insulators are very effective at trapping air, each individual filament of fibre is spiralled with 4 hollow cores which significantly increases the ability to trap air. The QXF3D fibre is lighter than ordinary solid fibre fillings. It is a high loft filling, which adds to its insulating abilities but it compresses effectively to minimise pack size. It retains its insulating properties even when damp and is an easy care filling that can be carefully machine washed.