Marmot Plasma 15 Review, the best three-season down sleeping bag

Max Neale, Review Editor for Outdoor Gear Lab, reviews the Marmot Plasma 15 and declares it the best all-purpose down sleeping bag available. Here’s why:

If sleeping bags were cars the Marmot Plasma 15 would be a Ferrari. With its sleek lines, high quality parts, and fine balance of performance and luxury, the Plasma 15 represents the best all-purpose down sleeping bag on the market.

Like a Ferrari, the Plasma is not the cheapest option. Those seeking value might look elsewhere, perhaps at something from REI. Nor is the Plasma the lightest sleeping bag. Go for a custom bag from Feathered Friends if you must save every gram. But for someone seeking a warm, comfortable, high quality and lightweight sleeping bag, the Plasma 15 is the ticket. It’s a bag you’re excited to carry, excited to climb into at the end of a long day, and it’s wonderfully versatile.

The Plasma 15’s combination of performance and comfort is what sets it apart form the competition. Other top quality bags, like the Montbell Ultralight Super Spiral Down Hugger #1, which has elasticized seams and stretchy fabric, are very comfortable but come up short on the performance end. That bag weighs a full six ounces more than the Plasma 15, and its elasticized seams have been problematic in the long-term. What the Plasma 15 contains that most others don’t is vertical baffles (tubes of down). Here, Marmot shifted the baffles from horizontal to vertical and added 7-8 Flow Gates (no-see-um mesh netting) to keep the down in place. The result is a wonderfully comfortable bag: the vertical baffles hug your body and move with you throughout the night. The Plasma is a bag you sleep with not inside of.

As for performance, the Plasma 15 rates highly. It’s stuffed with 900-fill goose down, the best and rarest on the planet. Why is 900-fil better than 700-fill? Answer: fill power measures the volume, in cubic inches, of one ounce of down. The higher the number the warmer and lighter the bag. 900 cubic inches is equivalent to the volume of four one-gallon milk jugs. With 17.6 ounces of down, the Plasma 15 is luxuriously lofty. Its shell material, Pertex Quantum, is also top quality and shockingly durable for its weight. These two materials make the bag warm, light and compressible. The Plasma 15 packs down smaller than a cantaloupe.

While down and shell material are the two most important components of a sleeping bag, finer design details also play an important role in a bag’s performance. Here, too, the Plasma excels. Most notable are its expansive foot box and ultra comfortable hood area. The Plasma has a full down collar that wraps around your neck and seals out cold air. This closes with two snaps (which are more reliable than velcro) and cinches tight around your neck with an elasticized drawcord. Down collars are crucial for when temperatures drop below freezing. The Plasma’s collar, which is both comfortable and effective, makes the bag viable down into the teens and below if used with insulated clothing. Another good thing about the hood: it has a tapered shape with a small opening that only needs to be cinched when the temperatures drop. Bonus: a small tube of down buffers the drawcord from your face. The Plasma has one of the few hoods that’s truly comfortable when the neck baffle and hood cords are fully cinched.

And for versatility, the Plasma’s generous fit accommodates a wide array of body types. Both men and women will find the bag to be a good fit. Its full-length zipper also makes it as functional on the floor of a friend’s house as at 14,000 ft. This is a critical point. Most ultralight bags have short, quarter-length zippers that limit where and when you they can be used. And other slightly lighter bags skip the draft collar, which makes them less good for colder weather. An example of such a bag is the Sierra Designs Cloud 15 ($500, 28 oz), which also has vertical baffles, is two ounces lighter, but lacks a draft collar (which makes it less warm) and has a short zipper that can make it too hot for the summer. The Plasma 15 is cheaper, warmer, and more versatile.

There are two potential drawbacks to the Plasma 15. First, vertical baffles limit its versatility because the down is fixed in place. (Continuous horizontal baffles allow down to be moved from the top to bottom of the bag, which—if attentively managed—increases a bag’s performance.) Second, the Plasma 15 isn’t the lightest sleeping bag out there. If you’re going ultra fast and light, where every gram counts, a custom bag or quilt style bag will save a few ounces. (The Katabatic Gear Sawatch is an option.) These drawbacks aside, the Plasma 15 is the best all-purpose bag available. It’s warm, comfortable, and lightweight. If you’re looking for one sleeping bag to do it all, the Plasma 15 is the ticket.

For clothing from Marmot, and other Marmot sleeping bags, browse our shop’s selection.

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