Do you remember that jingle “Come see the softer side of Sears”? Well, I’d like to invite you to see the lighter side of Sea to Summit.
Sea to Summit has produced an impressive catalog of lightweight gear in the past few years. It wasn’t long ago when their shelter offerings were limited to a tarp-poncho (nice and still available) and a rather small, heavy tarp (passed away). And while they offered several travel and sleeping bag liners, sleeping bags were not yet in their lineup.
Today they offer a wide range of outdoor gear including fully-enclosed shelters, packs, and sleeping bags. They have much more available than the scope of this article will allow – so check them out yourself to see their extensive product line.
Sea to Summit has definitely caught the lightweight bug. Their soon-to-be-released 12.3 ounce Spark SpI sleeping bag will vouch for that. The down fill in this bag weighs more than all its other materials combined.
Another impressive sleeping bag and subject of this article is the Sea to Summit Micro McIII.
The McIII is a 3-season mummy-style, box-quilted, sleeping bag with a differential cut shell and (convertible) drawstring footbox. It sports a draft tube with an anti-snag YKK #3 zipper system, a hood with dual adjustments, and a generously sized internal pocket.
Sea to Summit Micro McIII Package
Down: Ultra-Dry Down™, 850+ Loft, 90% Down cluster, premium European Goose Down
Fill weight: Regular 350 g/12 oz | Long 380 g | 13 oz
Bag weight: Regular 710 g/1 lb 9 oz | Long 780 g/1 lb 12 oz
Length / zip options: Regular – right zip | Long – left zip
Season Ratings: Spring/Autumn/Winter, EN Rating (Lower limit) 28F/-2C
The McIII is distributed with an Ultra-Sil compression bag, mesh storage cell, and a laundry bag (with printed care instructions on it).
Personal Weight Verification
My calibrated scale indicates that a regular McIII weighs 25.4 oz. It’s advertised on the tag as 25 ounces, so that’s close enough for me. As I’ll demonstrate further in this article, the features and versatility of this sleeping bag are worthy of its weight.
The included Ultra-Sil compression sack weighs 2.05 oz. This may come in handy for those with minimal pack space available and that could benefit from substantial compression.
Some backpackers (including myself) do not use “compression” sacks but instead opt for a lighter, waterproof sack. A couple alternatives include an Ultra-Sil Dry Sack (8L) at 1.15 oz or a Turkey-Size Oven Bag (19” x 23.5”) at 0.50 oz. The dry sack allows for moderate to significant compression, and the turkey bag offers minimal compression while providing enhanced distribution in the pack.
Sea to Summit Micro McIII Footbox Open (Temperature Regulation Mode)
I’m impressed with the detail that Sea to Summit has put into this sleeping bag and the included accessories.
They’ve included a zippered, net stow bag that is great for handling and storage. A cotton laundry sack that has comprehensive care instructions printed on it. And there’s even an informative letter by Sea to Summit founder Tim Macartney-Snape (mountaineer and author) and a copy of the “Down Batch Test Report” from the International Down Feather Laboratory (IDFL) which are nice touches to further complement the product. [More on this later.]
Sea to Summit Micro McIII Security Pocket
Goose Down / Box Quilted
The McIII has 850+ fill power Ultra-Dry Down™. The Ultra-Dry Down™ has a “nano-thin” anti-bacterial/microbial treatment that is said to absorb 30% less moisture and retain over 60% more loft than does untreated down – without effecting weight or loft.
While I’ve seen more geese in the cold water than I have in the dry desert, I do appreciate the extra effort to enhance the insulating quality of down when wet. I’ll continue to protect my bag from sweat, condensation, and precipitation as best as I can. But the added (potential) protection is certainly a welcome bonus.
There are few companies that I trust regarding the goose down in their products. Each of them observe strict standards and subject their down products to independent laboratory (e.g. IDFL) testing and certification. More than a few bags that I’ve scrutinized do not have the quality of down that they are said to have. I can actually feel the lack of loft and empty space in the baffles. When held to the light, downless voids, that translate into cold spots, are readily visible.
One thing that I want you to take from this article, above all else, is that it’s imperative that you don’t blindly accept the numbers (e.g. 800 fill,…) on a bag, tag, or in an outdoor rag (magazine). Demand proof in the form of reputable third party testing and certification.
Did you know that some down products (sleeping bags) may contain immature down? That is, it’s from early moultings which produce fragile down that will not hold up (loft, endure) as will mature down. Mature down is lighter and has the attributes to provide more warmth. As geese mature their down forms tiny hooks that enable the down to cling together which further enhances its insulative property when used in sleeping bags.
Sea to Summit Micro McIII Duvet Mode
The McIII is box-quilted with 3 dimensional baffles (not sewn through). This construction ensures that the down stays where it belongs and minimizes heat loss through seams.
The shell fabric is cut larger than the lining. This differential cut allows the down insulation to achieve optimal loft.
Sea to Summit uses the EN13537 European standard for sleeping bag temperature ratings. The “standard” is an effort to standardize ratings and offer consumers essentially three temperature ratings – namely Comfort, Lower Limit, and Extreme.
These ratings are applied to what is referred to as a standard man and a standard woman. As a guide, a standard man is defined as a 25 year old, about 5’ 8” tall, and weighing about 160 pounds. A standard woman is a 25 year old, about 5’ 3” tall, and weighing about 132 pounds.
In short, Comfort is the temperature that a “standard” woman can sleep comfortably; Lower Limit is the temperature that a “standard” man can continuously sleep for eight hours in a curled position; and, Extreme is the minimum temperature rating that a “standard” woman can essentially live for six hours without freezing to death.
Keep in mind, these standards are merely baselines that serve to compare ratings and specs. For example, they make it somewhat easier to compare the rating of one company’s sleeping bag with that of another.
There are several variables to consider regarding these standards and ratings including but not limited to age (older people might sleep colder), individual metabolism, medical condition, and level of physical fitness. It’s important for the individual to test and know her/his own personal requirements for warmth.
The McIII has a Comfort rating of 39°F, a Lower Limit rating of 28°F, and an Extreme rating of 0°F. If I were to classify the rating of this bag by the old (non-standard) method, I’d roughly list it as a 30°F bag – which doesn’t mean much and is subject to individual testing. I suppose the “standards” at least allow one to basically compare from product to product.
Sea to Summit Micro McIII Hammock Top Quilt Mode
The 2D NanoShell grey fabric is currently the lightest that Sea to Summit uses in their sleeping bags. The McIII shell utilizes this lightweight, breathable, water-resistant fabric.
A special DWR application features nano-sized particles that demonstrate an ability to better adhere to the fabric and thereby enhance the longevity of the water-repellency (1000mm) while maintaining significant breathability (>7,500 g/m2/24hr).
In practical terms, this shell does a good job at both keeping external moisture (snow, rain) out and allowing internal moisture (perspiration) to escape via micropores in the fabric’s water-repellent, breathable coating.
The down-proof lining is soft, black 20D polyester with a cire finish.
The hood differs from those on most other sleeping bag, in that it’s essentially a down-filled flap that takes on the shape of traditional hood when the dual-adjustment drawcord is used to form and fit it as desired.
Sea to Summit Micro McIII Footbox
Sea to Summit lists the primary use of the drawcord foot closure as means to regulate temperature. Useful indeed. I’ll offer a couple more uses that I’ve found to be practical. I call them camp mode and hammock (top quilt) mode.
Camp mode involves wearing the McIII like a jumper with both feet (shoes) freely outside of the open foot. Wearing a typical sleeping bag around camp would be like being in a sack race. Stumbling is likely. The drawcord allows the foot to be open for sitting, standing, and walking without damaging the bottom of the bag.
Hammock mode is using the McIII as a top quilt with a footbox. Simply cinch the drawcord and zip the bag up from the bottom just enough to form a secure footbox. Put your feet in the footbox, drape the quilt over you, and tuck the sides between you and the hammock walls as necessary.
There is a potential issue with hammock mode and the distribution of down. Because the McIII has more down fill on the top than the bottom (when in sleeping bag mode), hammock mode will result in a slight asymmetrical down distribution. Those interested should experiment to see if hammock mode meets their needs.
Sea to Summit Micro McIII Camp Mode
Though I have more in store for testing and using the McIII, the trips and experiences that I’ve had with it thus far have been positive.
I really appreciate the premium down and how it lofts. It’s warmer than other sleeping options that I’ve used with the same amount of down fill. I attribute this, primarily, to a couple factors: quality of down and baffle/quilting construction.
I’ve yet to push this bag to the limits, to observe its failure point (at least for me). But no matter how much experience I share, my shoes may not fit your feet. That is, there are a number of personal variables that need to be factored in to determine if this bag will meet your individual needs and applications.
For me, being 6’ tall with broad shoulders and weighing just over 200 (muscular) pounds, the McIII is somewhat snug. It’s not overly tight, but I better not gain any more weight. Sea to Summit offers a larger version of this bag and other models.
If I were to make any personal changes to the McIII, I would nix the hood and the 55/45 fill ratio. I’d use any weight/material savings from the hood removal to apply to enlarging the bag and for adding a top closure option.
Since the McIII also functions as a duvet (quilt), an even (50/50) down distribution is complementary to the design. A multi-use item such as a beanie or balaclava could be used instead of a hood. I realize and appreciate that some prefer the coverage of a hood, but a growing number of backpackers are sleeping without one for 3-season camping.
I trust Sea to Summit though not blindly. Like all of us, a company learns as it goes. We’re all subject to mistakes or misdirection.
It appears to me that Sea to Summit realizes this and has experts such as the IDFL verify their sleeping bags. I like that.
I can say with confidence that Sea to Summit has a great deal of integrity and quality built into the McIII. And this isn’t merely touted by zealous store clerks, it’s independently tested and certified by the world’s leading experts.
Surely I have the final say in how the McIII or any other product works for me and the same “say” rests with you.
If you’re looking for a lightweight 3-season, high-quality down sleeping bag, see if the McIII meets your criteria.