In colder conditions, when overnight temperatures started to approach freezing, we did start to get cold – but here, the mat was the culprit, not the bag. Upgrading to a warmer mat (in our case, a NEMO Tensor Insulated pad, with an R-value of 4.2) hugely extended the viable temperature range of the Cloud 800 20F. The fit is excellent with lots of room to move about. I would classify it as a wider than normal mummy bag. I'm 6' tall and the fit is perfect. The added foot vents are a nice touch when you need to cool off a bit but don't want to fully get outside the bag. The Sierra Designs Cloud 800 35 features a zipperless footbox vent, and zipperless comforter design making it very easy to lounge around camp while wearing the bag itself as an insulation layer. The construction is well made although the fabric is lightweight so you'll have to be a bit carefully with handling. Unless you are really rough on your gear there's no reason this bag won't last for years to come. Fabrics: Surrounding this high-quality insulation is a lightweight 15D nylon ripstop fabric. This lightweight fabric coupled with the down insulation results in a total weight of just 880g in this regular version.

I was really skeptical with the zipper-less design of the bag but it proved to be a non-issue. It's quite a warm bag but I'm generally a warm sleeper so I may not the be the best gauge for that, but it seems to do the job well in that regard. When it comes to specs, the bag is filled with 419g of 800-fill power moisture-resistant DriDown. The downfill is zoned, by which we mean it is strategically placed on the top and sides of the bag. Conversely, the underside of the bag has no fill at all. The brand’s rationale is that placing down fill here is of limited value since it is compressed by the user’s own body weight, negating its loft and, therefore, its insulating power.

Where to Buy

However, the EN 13537 European Standard does not apply to down-filled sleeping bags with a fill weight of more than 800g; for those bags, you will have to rely on the manufacturer's experience and technical expertise, which is often more accurate!

Comfort Limit Rating: This is the lowest temperature at which an average male should experience a comfortable night’s sleep whilst laid down in a curled up position. Bottom line, I love the concept, and I would much prefer it over a conventional mummy bag, I just wish the bag would be snugger, with more down in vital areas. We paired this bag with one of Sierra Designs’ Granby Insulated Air Mats, which has an R-value of 2.1. This ensured that the bag was plenty warm enough for late spring, summer and early autumn camps. The high-quality 800FP moisture-resistant down lofts well, being housed in chunky box-wall baffles. The quilted flap can also be pulled right up to the chin, ensuring we experience minimal heat loss. Design pros and cons: The sleeping bag is much more comfortable than a conventional mummy bag, the comforter does act like a blanket giving versatility to your sleeping positions. But side sleeping is comfortable only on your left side where you can move the comforter out of your nose and mouth; on the right side this is not possible, so you must sleep with your head over the hood. The hood is fitting ok, but not great, meaning it’s too wide and sometimes hard to find the right position to have your head covered.The Sierra Designs Cloud 800 35's zipperless design and oversized comforter can help one find solace after a long day of hiking. Synthetic fabrics used for outdoor gear are often ripstop, a textile weaving technique that provides materials with abrasion resistance. Ripstop fabrics have a visible grid-like pattern of threads that protects against snags and scratches—sort of like wired glass. While ripstop doesn't make a piece of clothing or gear invincible, it certainly helps lengthen the lifespan of a product and prevents from accidental cuts from your camping knife or a sharp tree branch. The Sierra Designs Cloud 800 35's generous comforter and zipperless design allows for a roomy fit around the shoulders. The Sierra Designs Cloud 800 35 features a generous pad sleeve to insert a sleeping pad in. To save weight, no down fill is located at the bottom of the bag where the pad sleeve fits.