With its high-performance goose down fill and lightweight, packable design, the Big Agnes Zirkel SL 20 Degree sleeping bag is designed for 3-season backpacking. A thermally-efficient and weight-saving mummy cut allow the Zirkel SL 20 Degree bag to weigh in at around 2.5 pounds.
The Zirkel SL 20 Degree bag is insulated with premium 800 fill goose down. Renowned for their compressible properties and efficiency in providing insulation, the feathers and fibers of down have an incredibly soft, comfortable feel and, despite advances in synthetic materials, continue to provide the best warmth-to-weight ratio of any insulation available. Though down fill is susceptible to the effects of moisture, losing much of its performance qualities when damp or wet, the Pertex Nylon shell fabric of the Zirkel SL 20 Degree bag is highly water-resistent.
Insotect Flow technology is used in the Zirkel SL 20 Degree bag to help eliminate cold spots, regulate the movement of down inside the baffles and offer better body heat distribution. Strategically placed Flow Gate construction eliminates lateral and vertical down shifting by using vertical chambers with Flow Gates to control the position and density of the down insulation.
In a traditional sleeping system, the bag lies on top of a sleeping pad. In this configuration, many people find themselves rolling off the pad at night. Plus, the insulation on the bottom of the bag is compressed by the sleeper's weight. Once compressed, the fill loses most of its insulating properties. The Big Agnes Sleep System is different, joining the bag and pad together. The pad slides into a sleeve on the bottom side of the bag, supplying insulation to the bottom of the bag while the top 2/3 of the bag is insulated like a traditional sleeping bag. This design provides a secure foundation so you can roll, twist and turn freely during the night without ever rolling off your pad. It also prevents the bag from twisting and engulfing you in an uncomfortable mess. Big Agnes uses this system throughout their entire line of sleeping bags.
The Zirkel SL 20 Degree bag is available in Regular (fits up to 5'10") and Long (fits up to 6'6") lengths. A half-sleeve design allows you to mate the bag with any mummy-shaped or rectangular pad so long as it isn't wider than 20". NOTE: Because the bottom of the Zirkel SL 20 Degree bag is completely uninsulated, it must be used with a pad of a suitable R-value in order for it to meet its 20 degree temperature rating.
A number of performance features equip the Zirkel SL 20 Degree bag for efficient insulation. A contoured, insulated hood keeps your head warm and a no-draft collar keeps cold air from creeping in the top of the bag and reaching the interior of the Zirkel SL 20 Degree bag. A full-length draft tube sewn behind the zipper further ensures that cold air remains outside of the bag. A no-draft wedge protects the connection between the bag and the pad, so that cold air doesn't sneak in between the two. A built-in pillow pocket holds clothes or a Big Agnes pillow (sold separately), providing a comfortable resting place for your head and neck.
A nylon stuff sack and recycled mesh storage sack are included with each Big Agnes Zirkel SL 20 Degree sleeping bag.
Sizes available: Long, Reg
Big Agnes part numbers: BZSLLL11, BZSLRL11