Even though it is two ounces heavier, we think the Western Mountaineering Summerlite is a much better choice for ultralight backpackers who prefer a hooded mummy. It is warmer for side and tummy sleepers, and it features a smooth operating, durable zipper. You'll find several more very light hooded mummies in our review of Backpacking Sleeping Bags.
The Mountain Hardwear MTN Speed 32 is one of the lightest products we evaluated in our Ultralight Sleeping Bag Review. It delivers a lot of warmth for the 16 ounce weight, but the cut is too slim for most hikers to wear their warm layers to bed on cold nights. In addition, with only a 32" side zipper, we feel this is the least versatile bag tested this year.
For our thin testers who sleep still on their backs, this bag is just a little warmer than the Western Mountaineering Summerlite. But for most of us, the Summerlite's additional girth also means we can wear our insulated jacket on colder nights without compressing the insulation. And the Summerlite has continuous baffles that are warmer for side and tummy sleepers. In short, we find the Summerlite (the competitor most similar to the Mtn Speed) warmer in practice for most backpackers. If warmth at a very light weight is your focus, we found that both the Katabatic Gear Palisade 30 and ZPacks Classic have better warmth-to-weight ratios.
On our digital scale, this mummy bag weighed in at exactly 16 ounces and the included stuff sack a half ounce. No doubt, this is impressively light for a bag this warm. As we understand it, Mountain Hardwear designed the Mtn Speed as a just-in-case bag for light and fast alpinists. Considering most alpinists will likely be carrying a warm down parka, we'd recommend carrying the similarly light Feathered Friends Vireo on alpine missions where you may or may not have to bivy.
We find this to be the least versatile product in our ultralight review. The partial length zipper limits your ability to open it up for hot nights and the narrow girth limits your ability to wear warm insulating layers on cold nights. For ultralight backpackers, we believe quilts, and especially fully-opening ones, are the most versatile sleep option. Our Best Buy award winner, the Enlightened Equipment Revelation 20 earned the highest versatility score we awarded.
This mummy bag received one of the lowest comfort scores, and it would have been lower still were it not for the comfortable hood and face opening. Actually, the hood is one of the highlights of this mummy — it has a down-filled baffle that is comfortable on the face when cinched up tight. Even though you may not need the added length, all but the thinnest of backpackers should opt for the long version of this bag due to its 4 inches of additional girth at both the shoulders and hips. You'll have a little more room to move around and add warm layers.
This mummy bag uses a 32" #3 zipper that is backed by a small draft tube. As we've noted, the poor function of this zipper is this model's main drawback. The hood closure of this bag stands out as very functional and comfortable. Independent cinch cords for the brow and lower part of the opening allow fine tuning and the down-filled baffles here are warm and comfortable.
This mummy uses one of the lightest shell fabrics out there and high quality water resistant down. Horizontal baffles on the top contribute to its warmth, and sewn-through quilting on the bottom saves weight. Unfortunately, the end of the footbox is also sewn-through. We were surprised not to see box baffles here. Two small hang loops sewn into the foot are a nice feature.
We do not recommend the Mountain Hardwear MTN Speed for ultralight backpackers, primarily because of concerns about the function and durability of the zipper. Some folks do love it enough to have the zipper replaced right from the start. If you do, this would be a good choice for thin backpackers who are back sleepers and want the lightest possible hooded mummy bag.
The Speed 32 retails for $480 but can often be found for less. Even on sale, we feel there is better value to be found elsewhere.
The Mountain Hardwear MTN Speed 32 is an impressively light mummy bag with a serious issue… the zipper is prone to snagging. Indeed, it snagged and then separated on our first test weekend.
The long version has 4" more girth at the shoulder and hip.