One way to reduce weight in a sleeping system is to use a top bag or quilt. The original Rab Top Bag that we reviewed in 2001 was a trend setter, reducing weight by letting a sleeping pad serve as insulation for the bottom of the bag. In 2005, the bag was upgraded to the Quantum Qtop, which featured a Pertex Quantum shell and lining, but we were perplexed by its excessively wide sleeping pad opening (wider than a standard twenty-inch-wide sleeping pad) and tight girth. For spring 2008, Rab is rolling out another upgrade called the Top Bag AR; does this one get it right?
The Rab Top Bag AR uses a sleeping pad for insulation on the bottom. Yep, the new version has a hood... well, sort of.
- Lightweight at only 20.5 ounces
- 850+ US / 750+ EU down fill
- Pertex Quantum shell and lining
- Baffled construction
- Well-designed pad sleeve fits a three-quarter or full length sleeping pad
- Adequate girth for a side sleeper without compressing down
What's Not So Good
- New "hood" is undersized and only useful for a back sleeper
- Narrow or short sleeping pads do not provide complete bottom insulation
- Four ounces heavier than its predecessor
- Temperature rating is optimistic
|2008 Rab Top Bag AR|
|Hooded top bag with bottom sleeping pad sleeve|
|Bag, stuff sack, storage bag|
|7 oz (200 g) of 850+ US / 750+ EU fill power down, underside of footbox is insulated with 133 g/m2 Primaloft|
|1.75 in (4.5 cm) single layer loft|
Manufacturer Claimed Temperature Rating
|30 °F (-1 °C)|
|Measured dimensions: 14 x 7 in (36 x 18 cm).
Manufacturer specification: 9.5 x 4.3 in (24 x 11 cm).
|Measured weight: 1 lb 4.5 oz (581 g).
Manufacturer specification: 1 lb 2 oz (550 g).
|One size fits to 6 ft (1.82 m)|
|Shell and lining are 0.9 oz/yd2 (30 g/m2) Pertex Quantum with DWR|
|Sleeping pad sleeve fits three-quarter and full length pads, hood, elastic drawcord top closure, Primaloft insulation under the footbox, box wall baffles, stuff sack, cotton storage bag|
When the original Rab Top Bag came out, it was one of the few pieces of ultralight gear that could be purchased directly at the time. It wasn't perfect, as our previous reviews have pointed out, but we were glad to have it available because the alternative then was to make our own gear. Now there are many ultralight down sleeping bags available, and hikers are carefully comparing features and performance to choose the right bag for their needs. The market is much more competitive now, so has the new Rab Top Bag AR reached perfection or not?
To answer that question, let's start with the likes and dislikes from our 2005 review of the Quantum Qtop. We liked its light weight (16 oz), high loft down, baffled construction, and Pertex Quantum shell and lining. Those features haven't changed. We disliked the Qtop's extra wide sleeping pad opening (wider than a standard 20-inch-wide sleeping pad), tight girth, and only one length. The first two problems have been fixed, but the last one (multiple lengths) hasn't. Three new features have been added: the underside of the footbox is insulated with Primaloft, a sleeping pad sleeve has been added to the underside, and the bag now has a "hood."
The underside of the new Rab Top Bag AR has a true pad sleeve made of Pertex Quantum fabric. It is fitted so a standard 20-inch wide sleeping pad (left), such as the Therm-a-Rest Prolite 3 Short (shown), fits snugly in the sleeve with no gaps on the sides to create cold spots. The sleeve has a clever extension (right) to accommodate a full length sleeping pad.
One thing to keep in mind is that the Top Bag AR does not work well with sleeping pads that are less than 20 inches wide and 48 inches long - such as the popular Bozeman Mountain Works TorsoLite. The TorsoLite is 17 inches wide at the top and tapers down to 12 inches wide at the bottom, so there are uninsulated gaps on both sides and the bottom end of the pad. The gaps won't be noticeable when sleeping at warmer night temperatures, but when the temperature falls below about 35 °F, the cold spots around the pad will be very noticeable!
The new Top Bag AR adds a hood (left), or at least a partial one. The hood is not large enough to completely enclose the head, as modeled by my wife Janet (right), and is only useful to back sleepers.
The Rab Top Bag AR still comes in only one length, which I measured at 62.5 inches to the bottom of the hood opening and 72.5 inches to the top of the hood opening. Rab states that the Top Bag AR will fit a person up to 6 feet tall. I am 6 feet tall, and the bag is too short for me when I draw up the hood, though the length is adequate if I cinch the drawcord around my neck and do not use the hood (I simply fold it under my neck and wear a warm hat at night, like I would with a hoodless sleeping bag.). My estimate is that the Top Bag AR will fit a person less than 5 feet 10 inches tall using the hood. Interestingly, the previous hoodless model (the QTop) measures 69 inches long (I had the extra girth version), which is 6.5 inches longer than the new Top Bag AR. Go figure.
I found it difficult to measure the loft of the Top Bag AR because the insulated sides of the bag wrap around to the edge of the sleeping pad sleeve, causing the bag to stand up higher on the sides and sink in the center. My best estimate of single layer loft in the chest area is 1.75 inches. Rab estimates the temperature rating of the Top Bag AR at 30 °F, but it is not based an independent test according to the EN13537 standard (it's not possible to conduct a standard test and get a CE label on a sleeping bag with no insulation in the bottom).
As for weight, the new Top Bag AR weighs four ounces more than the previous QTop, which I assume is mostly due to the addition of a sleeping pad sleeve, hood, and Primaloft insulation under the footbox.
Underside of the Rab Top Bag AR, head end (left), and foot end (right) with a full length sleeping pad.
The Rab Top Bag AR comes with a roomy Pertex Quantum stuff sack. The stuffed bag measures 14 x 7 inches, but can be stuffed into half that volume if desired.
I field tested the new Rab Top Bag AR on a number of mountain backpacking trips in late summer and fall 2007 and spring 2008. In each case I slept in a single wall tent, with low temperatures ranging from 24 to 42 °F (measured with a Kestrel 4000 Weather Tracker). I consistently got chilly at about 35 °F and had to put on more clothing to stay warm the rest of the night.
I found the girth of the new Top Bag AR more to my liking than the QTop. While the previous QTop bag was too tight for side sleepers, especially in the hip area, the new Top Bag AR has adequate girth to accommodate side sleepers wearing lightweight insulated clothing inside the bag.
While our Backpacking Light Position Statement on Sleeping Bag Temperature Ratings emphasizes that there are many factors that affect a bag's warmth, I would like to present the following data to compare the Rab Top Bag with other popular ultralight down sleeping bags.
|Manufacturer||Model||Temp Rating (°F)||Single Layer Loft (in)||Weight of Down (oz)||Fill Power||Total Weight (oz)||Cost|
|Montbell||Super Stretch Down Hugger #3||30||?*||10||800||23||$270|
|Rab||Top Bag AR||30||1.75||7||850+||20.5||$200|
*At the time of writing, this information was not available.
As you can see from the table, a high quality baffled 30-32 °F down bag contains at least 10 ounces of high loft down, giving it about 2 inches of loft. The Top Bag AR is not insulated on the bottom, so that saves some down, but the loft is a bit deficient. That may explain my late night chills when the temperature dropped below about 35 °F, but isn't definitive. On the positive side, I had no problem staying warm down into the mid 20s °F in the Top Bag AR when I wore extra clothing, which was usually a Bozeman Mountain Works Cocoon Pullover and Pants.
While I can't state that the Rab Top Bag AR has reached perfection, it certainly has come closer with its new sleeping pad sleeve that will snugly accommodate either a three-quarter or full length twenty-inch-wide sleeping pad. Using this bag basically commits a person to use a standard width sleeping pad in order to get a tight seal. An ultralight pad can be used in warmer temperatures, but it will have cold spots along the sides and end of the pad in colder temperatures. It would be nice to add another ounce of down to this bag to achieve a solid 30 °F temperature rating.
The girth of the new Top Bag AR is now adequate to accommodate side sleepers, but the bag's shorter length will be a deterrent to hikers at or over 6 feet tall. The hood provides some benefit to shorter hikers (it only partially covers the head), but it is of little use for taller hikers and side sleepers.
Finally, as seen in the above table, the Rab Top Bag AR is an excellent value at $200 for an ultralight sleeping bag, compared to the competition.
To save weight, the Rab Top Bag AR is not insulated on the bottom. Rather, it relies on a sleeping pad to provide insulation along the bottom of the bag.
Recommendations for Improvement
- Offer the bag in regular and long lengths.
- Add another ounce of down.
- Re-design the hood to fully cover the head, so it can be drawn over the face.