Under different circumstances, the cold rain and heavy condensation in the Smokies would have been trying. The constant drip would have soaked most down sacks, but two testers slept dry in bags with Pertex Endurance shells. In testing for the better part of a year, from the Smokies to Alaska, we found Endurance to be the most effective weatherproof/breathable sleeping bag material we''ve ever used. A coated fabric, it sheds water like an umbrella, is tough as armor, and boasts excellent breathability. Unlike Mountain Hardwear''s Spectre SL, most bags with Endurance aren''t seam sealed, which means less success in full-on rain (the exception: Exped''s Endurance bags are seam-sealed, but cost significantly more than the Spectre SL). It''s also less crinkly and noisy than other water-resistant shells we''ve tried. Endurance is slightly bulkier than a standard microfibre shell and adds a few bucks (about $60, give or take) to a bag''s price, but anyone who wants dry down in inclement conditions should give it a look. Endurance is available on bags from Exped, Integral Designs, Moonstone and The North Face.

A near-custom fit with nine size choices, plus a weather shedding shell and a flock''s worth of down, makes this bag a winter haven for sleepers who like their sacks'' dimensions to be just right.

Even during the worst weather our testers experienced, on a cold and wet expedition to Alaska''s Mt. Hunter, the XPD2 lofted up night after night, thanks to 40 ounces of 750: fill-power down and the weather-resistant Pertex Endurance shell. Heather reported nothing but warm temps down to -25oF.

Testers praised the bag''s details, like an overstuffed draft tube and deep hood that eliminated cold spots, and a roomy but efficient cut that let sleepers toss and turn without wasting warmth. (We tested the "relaxed fit" width.) A clever feature is the removable draft collar, which Matt appreciated because he could easily shake off condensation that formed from his breath. The larger-than-average footbox left some testers appreciating the extra wiggle room, but 5''6" and small-footed Heather found it too spacious. Length is dead-on, so consider a longer-than-normal size if you like extra length in a cold weather bag. The tuck-stitched baffles (hides and protects the thread) kept the down from shifting even on extended expeditions and the Pertex Endurance shell withstood months of abuse.

Versatile in wet conditions, the synthetic-filled Primaliner adds a second layer of warmth to another bag but also functions well as a standalone bag to about 10oC. A snugly contoured mummy design maximizes efficiency, and a parachute fabric keeps packed size down to a bare minimum.

"After a century of trying, man still hasn''t successfully mimicked the warmth-to-weight genius of down. (It took Mother Nature several million years of prototyping.) The XPD-00 - another premier product from Integral Designs, a small equipment company run by a clan of fanatical, ounce-counting Canucks - is your home-away-from-home when traveling light. Stuffed with 750-plus-fill European goose down, and featuring trapezoidal baffles, a fat collar, and an ergonomic hood and foot section, the XPD-00 will keep you locked in your sweet dreams right down to 20 degrees."

"For an overnight trip, Jon fit the Primaliner into a fannypack - no surprise, given that this was the lightest system we saw. Despite the minimalist size, I was pleasantly surprised at the warmth of both bags on a night near 0oF in Idaho''s Boise National Forest: I wore only a jersey and long underwear - not even a hat. The 50oF Primaliner fits nicely inside the 20oF Appalachian without the outer bag constricting the inner, creating a system rated at 5oF The high-lofting Appalachian, overstuffed with 750-fill-power down, boasts an ample draft collar. Both Integral Designs bags vent well, thanks to full-length, two-way zippers. Neither lost loft after laundering, and the Appalachian features tuck stitching, which conceals the stitches, protecting them. The Appalachian''s Pertex Microlight shell equaled the best in the test for repelling wind and condensation. We also loved the waterproof and superlight silicon coated stuff sacks. Our main gripe with the system was fit. The Primaliner has a claustrophobic cut, and Jon reported the size long Appalachian too roomy for him to heat efficiently. Ultimately, these bags, used alone or together, were not quite as warm as the Western Mountaineering combination, though they were less expensive and a few ounces lighter."

"Up in Calgary, they know a thing or two about cold weather, as evidenced by this bag. Featuring ultralight fabric, high-quality down and an efficient design, the XPD2 has a lot to offer at a reasonable price. The nicely contoured hood has a face seal, the foot section is shaped better than many and the nesting draft tube seals nicely without snagging. The plump down collar is removable for warmer conditions. This is the only bag in the review with no side-block baffle, allowing the down to shift from top to bottom, nice for summer bags, but I would prefer extra down control in something this warm. The XPD comes standard with 750+-fill and a Pertex Microlight ripstop shell. The bags come in three widths and three lengths; custom sizes are available too. Vapor-barrier and silk liners are offered. However, no method of attaching them is provided. If you are going someplace really cold, the even loftier XPD3 (-40oF) is available."

"This little bag is extremely versatile for climbers involved in all elements of the sport. On it''s own at 10oC it can be used for staying at the Skaha hostel or for a summer sleep out at Lion''s Head. As a bag liner it adds 15oC and will convert many three season bags in to winter bags. If it is taken with a bivy sac you have the makings of a light weight alpine bivy With a packing size of 4" x 12" and at 570grams this Primaloft bag is small and meets many climbing needs"

"For an overnight trip, Jon fit the Primaliner into a fannypack - no surprise, given that this was the lightest system we saw. Despite the minimalist size, I was pleasantly surprised at the warmth of both bags on a night near 0oF in Idaho''s Boise National Forest: I wore only a jersey and long underwear - not even a hat. The 50oF Primaliner fits nicely inside the 20oF Appalachian without the outer bag constricting the inner, creating a system rated at 5oF The high-lofting Appalachian, overstuffed with 750-fill-power down, boasts an ample draft collar. Both Integral Designs bags vent well, thanks to full-length, two-way zippers. Neither lost loft after laundering, and the Appalachian features tuck stitching, which conceals the stitches, protecting them. The Appalachian''s Pertex Microlight shell equaled the best in the test for repelling wind and condensation. We also loved the waterproof and superlight silicon coated stuff sacks. Our main gripe with the system was fit. The Primaliner has a claustrophobic cut, and Jon reported the size long Appalachian too roomy for him to heat efficiently. Ultimately, these bags, used alone or together, were not quite as warm as the Western Mountaineering combination, though they were less expensive and a few ounces lighter."

Summary:
The Andromeda Strain was a solid performer in our field testing. It is a great choice if you think either you or your bag are going to get wet. It was tops for drying out wet hikers and their clothes overnight and retained only minimal moisture in the process. However, the bag''s specifications (loft and temperature rating) were not quite up to the manufacturer''s claims. Sadly, the same can be said of many other synthetic and down sleeping bags on the market. Please see "Sleeping By Faith: Bag Temperature Ratings," also in this issue. If Integral Designs made a bag with 2" of actual total loft, and the loft distribution was altered to provide more on top, we think the bag would be a winner in the synthetic category. Because the bag is designed for moderate temperatures and by its nature should be lightweight, we appreciated the use of Pertex Microlight in the shell and lining, but we would have liked to see a lighter, half-length zipper as the standard option. Final Grade B A good design and quality materials and workmanship are the Andromeda Strain''s strong points. The bag excels in wet conditions and weather that is not too cold. We think the Andromeda Strain could be an even better and warmer bag with a bit more loft, better distribution of loft, and a better fitting hood.

Full Review

"The only model with Primaloft insulation, this is one of the lightest bags, and it is more compact than any other in the review. (also the most expensive), yet has a roomy cut. It doesn''t look as warm as the rest, but I found the rating accurate. This would be my top choice for demanding alpine climbs. A broad width option adds five inches to the girth."

"Integral Designs is an innovative Canadian company specializing in lightweight gear designs for mountaineering and other outdoor adventuring. Their synthetic-fill sleeping bags make use of Primaloft Sport insulation, which is perhaps the most thermally efficient and water resistant of the polyester fiberfill''s. The North Twin is a truly three-season bag that would be a good choice for paddling expeditions into cold and wet environments.

The various features seem to be carefully designed to maximize comfort at colder temperatures. The interior of the bag is roomy enough, at least for people of average stature, while maintaining an efficient fit to trap in warmth. The draft collar and hood arrangement can be fine-tuned around your face and neck to minimize heat loss. The shape of the foot area is tilted to conform to the position of your feet while you''re lying on your back. The two-way zipper operates smoothly and didn''t catch or snag. The loft or thickness of the bag varied from the 10-degree rating more accurate for men than women, in my opinion. And finally, the Pertex outer shell material, while not waterproof, has the ability to resist wetting from drips and wet spots that might occur in a leaky tent."