This summer I order the swallow ul 20 from feathered friends after playing with an array of sleeping bags over the last 5 years. My previous long term bag was a Marmot helium that I had for over a decade, but as it began to wear out I tested a variety of options. In short, this will be the bag that I see myself settling into for many years to come.To start my search about 5 years ago, I used a western mountaineering highlite. The bag was phenomenally light, and as well made as a guy could hope for, but after a season of alpine use in the shoulder seasons it was farm from warm enough. A lot of nights with little sleep and all my clothing on led me to sell this bag off the following year.After that I migrated to a synthetic option, which I found in the Kifaru Slick Bag. This sleeping bag is phenomenal in its own right, and is the only serious synthetic bag option that I would recommend to anyone for serious backpacking. Being tough as nails, and conservative in its 20 degree warmth, it works exceptionally well.The real advantage to me in terms of synthetic is being able to sleep in wet clothes and wake up in the morning with them dry. I found through my use with it though, that I am more than capable of keeping a bag dry, even in wet conditions as long as I am disciplined. The real downfall to the slick bag for me isn't the weight, but rather the bulk. Using a synthetic bag pushed me into backpacks that were much larger than I prefer in order to accommodate the bulky sleeping bag.Enter my next purchase, which was an enlightened equipment down quilt. When I started testing it in warm weather, I really loved the quilt. However, as temps got colder I just couldn't seem to cut the chill. The 10 degree quilt would leave me cold from about 35 degrees and below.The small size and very light weight of the quilt were appealing, but in the end it wasn't quite doing the job that I needed it to. I did get better at sealing out the draft, but I still found myself dealing with cold air in the middle of the night.So once again I went on the hunt and purchased the Feathered Friends Swallow UL 20. After 30+ days in it this fall, I've finally found what I was looking for. The down fill used by feathered friends is second to none, and better than what I've seen in any other bag I have owned or looked at in person. The loft of their 950+ fill is incredible.In addition to the quality of down, the pertex endurance shell fabric is very down proof, as well as wind and water resistant. The wind resistance means a lot to me as I spend a large amount of time under a tarp. Cutting the wind chill out makes a big difference at night.As would be expected with such high end down and textiles, the bags packed size is minuscule for what it provides, and it allows me to go back to a pack that is much more appealing to me in terms of overall size on my back.Personally, I like a slim fitting bag to cut weight and bulk, and to help insulate efficiently while sleeping. I will note though, that for a standard width bag, this one is on the slim side. For me, it fits well, but for someone who likes some room I would strongly suggest a wider model than the swallow.At slightly over 1.5 lbs, this bag is easily suitable for me down to the 20 degree rating and has a full length zip which is pretty impressive. For a 3 season sleeping bag, this one would be tough to beat. Granted, such an impressive piece of insulation comes with a hefty price, which is the only real downside of this bag. Another important side note though is that down bags can last a really long time, as in over 10 years of heavy use. For me this is enough of an incentive to pay for a very high end bag that will see hundreds or more days in the field during its lifespan.All in all, I would put this bag at the top of the list on any that I have used. The true top shelf components that it is made of set it apart from anything on the market except from possibly western mountaineering. There's a reason that I prefer to buy down products from companies that only make down gear, and the swallow UL 20 is a great example of why.If you're in the market for a sleeping bag you can also read my previous article on Sleeping Bag Selection. Also if you're looking for a top shelf sleeping bag for backpacking, give feathered friends a look. Their full line of bags and down garments (which are equally as good) offer some of the best there is.