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Western Mountaineering Summerlite Sleeping Bag REVIEW

Hooded, down mummy bag rated to freezing that weighs a mere 19 ounces.

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by Don Wilson | 2006-12-19 03:00:00-07

Western Mountaineering Summerlite Sleeping Bag REVIEW - 1


Western Mountaineering introduced the Summerlite sleeping bag to the US market in January 2006. With features focused on three-season performance and light weight, it instantly drew attention from ultralighters. The Summerlite is the lightest fully baffled bag in Western Mountaineering’s lineup. It has a full-length zipper, insulated draft tube, 4 inches of double-layer loft and weighs 1 pound 3 ounces for the regular length. The long length bag has a specified weight of 1 pound 5 ounces (1 pound 5.4 ounces as measured). The Summerlite is part of the Extremelite series and uses a 0.9 oz/yd2 Extremelite shell fabric. In 2007, Western Mountaineering will offer a new short length version designed for people 5 feet 6 inches or less. This version will likely come in near a scant 1 pound 1 ounce. I used the Summerlite for 6 weeks on the Pacific Crest Trail this summer and have some strong opinions about its combination of features and performance. The picture at right was taken on a winter trip in Aravaipa Canyon, Arizona.

The Summerlite has an interesting history as described by Gary Petersen, Production Manager for Western Mountaineering. This bag was originally developed at the request of a European dealer who is a long time customer of Western Mountaineering. The dealer approached Gary in 2002 with a request for a very specific bag - a 32 degree F bag (0 C), in a narrow mummy configuration with a full-length zipper and a target weight of 1 pound 3 ounces (550 grams). They initiated production of the bag in 2003, but did not make it available worldwide until January 2006. It was immediately popular and is already one of the top ten selling products for Western Mountaineering.

What’s Good

  • 1 pound 3 ounce sleeping bag with three-season warmth
  • Full zipper is convenient and improves versatility
  • Baffled construction, an unusual feature at this weight, reduces cold spots
  • Narrow mummy configuration with hood
  • Stuffs into 12 by 6 inch stuff sack

What’s Not So Good

  • Might be a little narrow for some



2006 Western Mountaineering Summerlite


Mummy (with full length zipper)


9 oz (255 g) 850 plus down (regular length), 10 oz (283 g) for long length

  Measured Loft

2.1 in (5.2 cm) single layer with down distributed evenly across the bag (continuous baffles allow loft to be adjusted); 4.1 in (10.4 cm) double layer averaged from measurements taken at the shoulder, hip and 16 inches above the footbox

  Manufacturer Claimed Temperature Rating

32 °F (0 C)


1 lb 3 oz (538 g, regular length), 1 lb 5.4 oz as measured, (606 g, long length)


Regular (to 6 ft, 1.82 m), Long (to 6 ft 6 in, 1.98 m), Short length (to 5 ft 6 in, 1.68 m) available in 2007


0.9 oz/yd2 (31 g/m2) Extremelite 20D nylon shell


Insulated draft tube, full length zipper, drawcord and hood, 5.25 in spacing continuous baffles


$280 (Regular), $295 (Long)


The Summerlite is intended to provide the most efficient warmth possible in a full featured three-season sleeping bag. It offers a full zipper to help regulate temperature on those warm summer nights, but with a full hood and insulated draft tube, is still efficient when pushing the bag’s performance into colder temperatures. I used my bag in a broad range of three-season conditions; winter nights in the desert, warm summer nights in the desert and foothills, and cold, wet alpine camps. I found the Summerlite to have a well chosen combination of features and efficiency. I have not developed a liking for top bags or quilts, and the Summerlite is the lightest and most versatile mummy bag I have used - and it can be used in the vast majority of conditions that I encounter.

Western Mountaineering Summerlite Sleeping Bag REVIEW - 2
The size long Western Mountaineering Summerlite has plenty of room to cinch up the hood for the author, who is 6 feet 4 inches tall. The hood is comfortable and easy to operate from within the bag.

Western Mountaineering Summerlite Sleeping Bag REVIEW - 3
For cold nights, the hood cinches up easily, but still leaves access right where you need it. There is no neck collar on the Summerlite.

The Summerlite is the lightest baffled bag made by Western Mountaineering. The baffles are continuous and wrap around the bag. With a little practice it is possible to move more down onto the top side of the bag, improving effective use of the down. This is easily done by unzipping the bag and pushing the down along the tubes from one side to the other. The baffled construction is a real advantage over sewn through construction, reducing cold spots and improving overall warmth. The baffles on the Summerlite are spaced 5.25 inches apart.

Western Mountaineering Summerlite Sleeping Bag REVIEW - 4
The Summerlite stuffs in a conveniently small volume. My sample bag is a size long; other sizes will of course stuff into even smaller volumes.

Western Mountaineering Summerlite Sleeping Bag REVIEW - 5
Baffled construction keeps the loft of the Summerlite nearly uniform across its length. Average double-layer loft on my test bag was just above the specified loft of 4 inches.

The Summerlite is cut in what Western Mountaineering refers to as a narrow mummy configuration. The internal girth dimensions are listed as 59 inches at the shoulder, 51 inches at the hip and 38 inches at the foot, for the regular size bag. These dimensions are identical to those on the Highlite and Ultralite models; two of the other lightweight bags offered by Western Mountaineering. I am used to mummy style bags and found the Summerlite to offer plenty of internal room. But I am also more lean than most. The Summerlite fits the description as a narrow mummy - if you aren’t a fan of mummy bags, the Summerlite may not be the best choice for you.

Western Mountaineering Summerlite Sleeping Bag REVIEW - 6
The draft tube on the Summerlite is stuffed with plenty of down to eliminate cool spots along the zipper. The #5 YKK zipper is light, reliable and is less abrasive than heavier zippers when material gets caught in the zipper.

The exterior shell on the Summerlite is Western Mountaineering’s Extremelite fabric. When developing the Extremelite fabric, Western Mountaineering looked for a combination of light weight, strength and uniform yarns that would make the fabric as downproof as possible. This fabric is a 0.9 oz/yd2 Pertex Quantum which has been calendared (heated and pressed between rollers or plates to smooth and glaze the fabric) on both sides. This sacrifices some breathability, but also reduces down leakage. According to Gary Petersen, uniform yarn sizes reduce down leakage since any junction where yarns of differing diameter meet is a likely spot for leakage. Ripstop fabrics have regular intervals with yarns of larger diameter, which improves strength, but can lead to leakage. That is why Western Mountaineeing has both sides of the exterior fabric calendared. The interior fabric on the Summerlite is a plain weave with uniform yarns (taffeta). By design it is more downproof, and is therefore calendared on only one side. It is likely that Western Mountaineering will use up their current supply of shell fabric and switch to new shell fabrics sometime in 2007. Any new fabrics will have similar construction and characteristics as the current fabrics.

Over the course of the summer I have spent more than 50 nights in the Summerlite and I have experienced almost no down leakage. The shell fabric is very light and I treat it carefully, especially if I drape the bag over bushes or grass to dry it out. I make sure to pay attention when I remove the bag from these situations, not dragging it across branches where it could get snagged or torn.

Missing from this review (and for all sleeping bag reviews published here, for that matter) will be an assessment of whether or not the sleeping bag performs adequately at temperatures near its manufacturer-reported temperature rating. Click here for the complete Backpacking Light Position Statement on Sleeping Bag Temperature Ratings.

What’s Unique

The Western Mountaineering Summerlite is a top quality, 19-ounce (regular size), 32 degree traditional mummy sleeping bag with a full zipper, draft tube and continuous baffles. No other bag on the market offers this combination of features and light weight. The Mountain Hardwear Phantom 32 and The North Face Beeline are similar (and a little less expensive) but the Phantom has box baffles and a three-quarter zip, while the Beeline has no zipper except for a foot vent. Nunatak presents a third option in the Alpinist which has a half-length center zip and 2.5 extra ounces of down for an extra $100.

Recommendations for Improvement

The Summerlite hits the mark for a very lightweight yet versatile three-season bag. Western Mountaineering has sacrificed some breathability to reduce down leakage by using Extremelite fabric. If they can find a fabric that combines improved breathability with similar downproof performance, the Summerlite could take another step forward.


"Western Mountaineering Summerlite Sleeping Bag REVIEW," by Don Wilson. (ISSN 1537-0364)., 2006-12-19 03:00:00-07.


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Western Mountaineering Summerlite Sleeping Bag REVIEW
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paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: Re: Re: Re: Marmot Bags and a question for readers on 12/21/2006 19:01:50 MST Print View

Mitchell, agreed. looks like we are both essentially on the same page. since questions about MB bags come up fr/time-to-time in the Forums, it would be very instructive to see how both a #3 and a #4 stack up to two other primo bags. are the criticisms of 725FP down justified? does the perceived lack of loft and thinness some have mentioned in the past really exist? [note: for my part my WM Highlite has less loft than my MB SSDH #3 by about 0.5".]

Mitchell Keil
(mitchellkeil) - F

Locale: Deep in the OC
Re: Marmot Bags and a question for readers on 12/21/2006 19:37:03 MST Print View

(Just cut down the re: re: on the subject line a bit.) I agree PJ. There are a number of us who own MB bags and the consensus seems to be that most of us are blissed out on them.(Not to mention blissed out on most MB product lines.) So why the constant drumbeat of concerns about 725 fill and inadequate loft and fill for the temp ratings? What I find very interesting is that in a Google search for MB bag reviews, very little has been written except by a few BPL members, me included. I have always felt that they are a great value for the $$ and spot on for temp ratings as well as very well constructed. They deserve to be put up against the best in the bag business -- Marmot, WM, Feathered Friends and the like -- and rated for comparison. So, I hereby request that BPL do a bag comparison to include MB. Any "Aye's" out there?

paul johnson
(pj) - F

Locale: LazyBoy in my Den - miss the forest
Re: Re: Marmot Bags and a question for readers on 12/21/2006 20:35:12 MST Print View

Oh well, i always wanted to be a Pirate, so...

Avast Matey, Aye, i be sailin' wit ya, Arrgh!

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
MY WM ALTERNATIVE TO THE SUMERLITE on 01/22/2007 11:00:41 MST Print View

I considered the Summerlite but got the Megalite instead.
I feel, with its slightly larger girth it would actually be cooler on hot summer nights but also allow for wearing insulated clothing on below 20F nights.
Plus, the Megalite has no side baffles so down can be shifted between the top and bottom to some degree. I've found that, once shifted your body weight keeps it in place.

So...for a few extra ounces I get greater versatility.

Oh yeah, I DID get a Mt'n. Hardwear Phantom 32 bag at REI 1st but returned it when I saw a WM Megalite in the flesh. The Phantom 32 had FAR less loft than the Megalite. The hard part was forking over the extra $100. for the Megalite. Now, after staying warm in the WM bag at 22F, I feel it is money well spent.
The Megalite also has a full length zipper which I feel is a MUST for hot nights.

Edited by Danepacker on 01/22/2007 11:07:42 MST.