Mountain Equipment starting making down sleeping bags in the early sixties when the sport of alpine climbing was still in its infancy. Since that time, it has stuck to what works while developing new technologies to perfect the art of making quality down bags that perform in the most demanding conditions. The Lightline SL 5 Degree Down Sleeping Bag incorporates both time proven technologies and modern innovations with minimum weight penalty, making it ideal for technical alpine climbs when ultralight is needed and a comfortable night's sleep is crucial to success. Since a comfortable night's sleep is key to recovery, Mountain Equipment developed a complex baffle system to minimize cold spots and optimize warmth while you sleep. Trapezoidal 2:1 ratio baffles are designed to stabilize the down while maximizing loft and increasing the areas of overlap between seams to eliminate cold spots. The hood of the bag incorporates eight zoned baffles to reduce the chance of down migration, while the anatomical fit helps to eliminate heat loss from the top of the bag. The Lightline also features the Gemini integrated draft collar for even more heat retention, as well as baffles behind the 34 length side zip to reduce draft. The foot of the bag utilizes a four baffle constriction designed to minimize weight while limiting down migration. The Mountain fit is a semi tapered mummy shape the blends both thermal efficiency with some wiggle room for comfort. Incorporating its EXL technology into the fit of the bag, the technology incorporates elasticated stitching within the lining, allowing the fabric to stretch for as much loft as possible studies suggest this technology accounts for an added two degrees of warmth with no added weight. The ground level side seams are placed lower towards the ground, so the upper baffles actually wrap around the side of the body allowing for a greater area of the bag to be unaffected by cold from the ground. The Drilite Loft II fabric is wat...