Passive Top Collar
Heat loss from the neck area is common while moving inside your bag at night. To stop this bellows-effect from pumping out warm air, our 3-season and winter taffeta bags are outfitted with our Passive Top Collar. This large 3-Dimensional baffle of down is fitted to the top inside shell and goes across your neck from the zipper to the bottom half of the bag. This construction provides a sure seal against the cold by passing the shoulder and making an air dam that would otherwise be missing if the collar were attached only to the top of the bag.

Extended Top Baffle
When bags are designed for the mild temperatures of summer use, the extra weight and bulk of a thick down filled collar is unnecessary. But just to provide extra security for the intrepid summer traveler we use our exclusive Extended Top Baffle on our Apache, Badger, and UltraLite. Simply put, the inside shell fabric is cut 1 1/2" to 2" longer than the outside top shell. This allows a larger down filled baffle right at your neck. This large top baffle is sewn with a single side block and is filled with extra down so that the baffle provides a better seal at the neck.

Super Collar
Bags for colder weather need a solid well insulated seal around the neck to guarantee warmth and protect against convectional cooling. Our Super Collar completely surrounds your neck with a 3-Dimensional down filled collar. That means the Super Collar has 2 seams that ensure a 3-Dimensional volume of insulation about your neck, rather than a cold, sewn-through, uninsulated seam as found on a flap collar. You'll find this robust collar on selected MicroFiber and DryLoft™; bags. This is the most substantial collar in the industry. To insure maximum moisture protection in our DryLoft™ bags, the draft tubes and all panels of the Super Collar are made with DryLoft™ fabric.

Reverse Differential Hood
In an effort to minimize heat loss around the exposed skin of your face our bags are designed with an oval cut Reverse Differential Hood. The inside fabric of the hood is cut larger than the outside fabric. This creates extra down filled fabric that fills about your face without cinching up the hood. This inside fabric can be shaped to form a hood ruff over your forehead.

Side Block Baffles
In cold weather you want insulation to stay on top of you without any chance of shifting. Our winter bags are built with a V-Block Side Baffle. This V-Block design does two things, it provides a wide pie shaped chamber of down along the right and left sides of the bag, and by increasing the number of chambers the size of the chambers are smaller. Smaller baffles provide better down control and the shorter baffles that cross your chest lie flat so that down can't fall to either side.

Differential Cut
Differential refers to the difference in circumference between the inner and outer shells of the sleeping bag. All of our mummy bags are differentially cut to promote proper lofting and to protect against down compression when knees or elbows push against the inner shell.

Continuous Baffles
A 3-season bag must serve in a wide range of temperatures. You expect to be comfortable during the heat of summer through the cooler temperatures of fall and early spring. To ensure a broad temperature range we build our 2 and 3-season bags with continuous baffles. This allows you to shift the down insulation from one side of the bag to the other. During hot summer nights, you could shift the down from the top of the bag to the bottom so there is less insulation on top of you. When the weather is cold, you can move the down to the top of the bag. Just open the bag flat and push the down with your hands from one side to the other. This adjustment allows a comfortable temperature to be maintained. By sewing these bags with 5 1/4" baffle spacing, unintended down migration is kept to a minimum.

Materials used in Western Mountaineering sleeping bags.

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