Nunatak Equipment - Sastrugi (18°F and 28°F variants)

I was gonna mention the Nunatak Sastrugi (big fan), but like the Timmermade false bottoms, it has a fairly narrow comfort window and perhaps not the most appropriate for an entire thru. Bags with full zippers and quilts are more flexible in regards to warmer nights.

(Edit: sorry about the over the top click bait title!) Ok… If you know me, my gear system is about maximizing comfort but still decreasing weight. Quilts have been a part of that system since 2017, but in 2025 they fail me in too many ways. 1)      Quilt straps are undeniably annoying. They get tangled, lost, they take time to position. It’s management time and I am lazy. I would rather watch that sunset, eat or just do nothing. 2)      Yes, a quilt reduces weight by removing unneeded backside material. However, because of the hole in the backside of a quilt, you must add back in straps, clip hardware, & hem reinforcement weight. Some manufactures even add tensioning systems to limit cold air ingress. It’s never made much sense to punch a big hole in something, only to add in weight in response to you punching a big hole in something. 3)      Quilts promise weight savings by eliminating traditional sleeping bag hoods, zippers, zipper guard tape, a draft tube backing up the zipper, and no unnecessary backside fabric/down. But, there’s a way to eliminate the first 4 of those and I’m going to show you why you actually WANT that backside fabric/down. 4)      Cold Drafts. I’m not saying drafts are overly frequent, but through the years they’re just not welcome anymore. I’ve heard deep ultralighters (sub 6lbs) talk about how they have trained themselves to just lay on their back all night. That is not how sleep is supposed to work. It’s good to toss and turn to keep blood moving through your tissues. However, when you toss and turn, air can make its way in. At 35F/2C or colder, it’s going to wake me up %100 of the time. Maximizing comfort means eliminating things that wake me up. There’s a better way to do this. But first, let’s address the number one advantage of quilts. Venting! You can loosen them and drape them over your body on a hotter night. There’s no disputing this great feature. However, if I am on a 5 day trip, maybe one of those nights may be “too” warm. I usually choose the right rating for the trip I am on. If more than 3 nights are excessively warm for the quilt, then I just brought the wrong gear. Thru hikers don’t have this luxury, but more on that in a second. The better way to stay warm, but not too warm, and still ultralight is… A simple hoodless and zipperless bag like the Nunatak Sastrugi (I have 2,) Feathered Friends Tanager, and now the Gryphon Gear Full length Elephant Bag (I just got a 40F/4C for hut hiking this summer.) [Go look at the Tanager right now](https://featheredfriends.com/products/tanager-cfl-20-ultralight-down-sleeping-bag?variant=20318841471030&country=US¤cy=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gad_source=1&gclid=CjwKCAiAn9a9BhBtEiwAbKg6fltZJpD6HJWLTnxsXD_uEcHtoU52V_jPJd9RXhcKx_4exF-d9fkTARoCoocQAvD_BwE) if you don’t know what I am talking about. It is NOT a traditional hoodless sleeping bag. It’s a simple bag that you slide your entire body, feet first, through the top opening. There is NO zipper and both the top and backside of the bag are the same. In other words, what you see on the top is what you see on the back (more on that in a moment.) This is what I have started to use and I like it… 1)      It’s cheaper to build, like $100 cheaper. 2)      There are no back side drafts because there’s no backside opening 3)      There are way fewer things to fail/tangle/lose/manage 4)      When you sit up on a cold morning, the bag is covering your back as you get ready for the day (thanks u/laurk) 5)      You still get the weight savings of no hood, no zipper, no zipper tape, and no zipper draft tube. 6)      But, here’s **THE BEST PART**, you get two different temperature ratings in one bag! You may not know this, but a lot of bag makers put a little less down in the back than on the top (that or you can shift the down with continuous baffles.) Some even change the baffle height (i.e. the loft) from top to back. Gary at Gryphon Gear confirms this on my new full length Elephant Foot bag. The topside baffle height is 0.4in higher than the back side. So, it’s indeed a two temperature sided bag. Here's what my testing has found. The 28F/-2C Nunatak Sastrugi is accurately rated on the topside. Now then, with the backside moved to sitting on top of my supine body, it's roughly good till 37F/3C, with the neckline cinched. Then, if I purposely move down to the side, it turns into 42F/5.5C (neckline is again cinched) and if I uncinch the neckline I’m good to about 48F/9C. At 48F/9C my feet start getting a little warm, as it's really tough to move down out of either side of a foot box. Note: I'm just wearing a tee shirt and short underwear. I'm also in a higher humidity area, just off a cold ocean delta. So in one bag, I have a 28F/-2C side, and a 48F/9C side. A **20 degree (F) difference in the two sides.** This should immediately sound great on those higher temperature nights I talked about above. This should immediately sound great to any PCT thru hiker wanting to know if they should get a 30F vs 20F quilt. Now, PCT hikers should absolutely get a 20F Simple Bag (can we please just call it a Simple Bag?) and they’ll effectively have a 20F and 40F bag all-in-one (depending on how the quilt maker designs the two sides.) I think continuous baffles are the way to go here. Despite my click bait title, not everything is perfect. AT thru hikers on a hot/humid night in Virginia? Yeh, you’ll probably want a traditional quilt. There are no absolutes here. You could pick a bag and add a little 20in zipper or go for a Enlightened Equipment Conundrum style. Although, it’s not like Simple Bags have ZERO venting. On a hot night at 8pm I would still lay there, let my core cool down, work the cooler side of the bag up to my knees, waist, chest and not cinching the neck line. Another con to simple bags, you will get some bellows action (hot air escaping) at the neckline. So be sure to get a neck baffle, but I consider that a must on any bag. Traditional quilts have plenty of this bellows action too through its openings. Lastly, you need to hit the mark on your body width. Do not under order the width or it will be too cramped.  TLDR: A Simple Bag (and no, this isn’t a traditional sleeping bag) keeps you warm by staying draft free and it has a warm side and a less warm side.  Ok. Thanks Attention: u/KatabaticGear u/EnlightenedEquipment u/Western_Mountaineeri 

lol. I moved the down, as Jan just said you can do. I now have a 28F sided bag and a 48F sided bag. Go move the down on your 18F then hold both sides up to direct sunlight. What do you see?

The Nunatak Sastrugi in 22F. If you redistribute the down you end up with a warmer 22F side and then on warmer days flip the bag over to the other side…. The other side turns into a cooler rated 32F side when cinched at the neck line. Keep the neck line open and in my testing you’re good to go-40F. You have ONE bag with a ~20F operating range that is draft free. No silly ass straps, no strap hardware to break, no added weight. Don’t get it with overstuff to make the redistribution above easier. Nunatak has 4 different temp ratings for a reason and Gryphon Gear will make one if you reach out. I have both. Gryphon even makes bags with a 60:40 split. If you’re sticking to Iceland, Greenland, and mountains above 5,000ft, there’s nothing better. Just don’t take it to tropical areas.

I did sleeping bags, then quilts (Nunatak & Katabatic,) and now it’s a Simple Bag like a Nunatak Sastrugi or a Gryphon Gear Full length Elephant Foot. They’re very good. These bags get rid of all of the unneeded weight and hassle of straps, strap hardware, zippers, draft tubes for those zippers and hoods; but eliminate the drafts that quilts have. No one I’ve ever met is going back and Nunatak has 5 temperature versions of the Sastrugi for a reason. Best part is… in one bag you can get a warmer temp rating on top and a cooler one on bottom. It’s two quilts in one. Gryphon Gear will even make one with a 60:40 split, so you don’t even have to move the down. So in one bag you can have 20F side and a 30F side. And if you keep the top open it will be good to 40F. One bag, with a 20F operating range… Nothings perfect though, if you’re in humid areas, just use a traditional quilts. But if you need draftless warmth, but still gets rid of needless items, there’s nothing better.

All the Sastrugi hoodless/zipperless bags as shipped have the same temp rating (ie loft) all the way around; and top to bottom. The user can if they want shift the fill to one side or another - not really something I bother with personally but with the continuous baffles it's doable. During use, combined with a laissez faire attitude towards down position maintenance, the fill can move away from areas as we all know.

Fellow rotisserie sleeper here. Mostly camp in my hammock but also go to the ground when I have to, e.g. routes above treeline. I’ve done quilts and mummy bags on the ground, and I don’t like either in their traditional forms. A third viable alternative is what basically amounts to a hoodless “bag” of some sort: a false bottom bag (Timmermade Serpentes/Wren), a zipperless bag (Nunatak Sastrugi), or a fully zippered quilt (Feathered Friends UL Wide Flicker). You have the option to select from a variety of sizes to suit your needs especially with Nunatak and Timmermade, but be aware of the lead times and specific ordering windows that will require some patience and diligence on your part. I find I sleep less interrupted in these types of bags on the ground, while traditional top quilts do just fine in a hammock system with an underquilt.

It's worth it. I bought a Flex 22 duck down and every humid night it stank like wet animal. Drove me nuts and I sold it and went with Nunatak goose down. I think goose down is worth every penny more just for the lack of smell benefits.