Sea-to-Summit Ascent Ac II Sleeping Bag Review (15F Degree)

Sea-to-Summit Ascent AC II Sleeping Bag Review

The Sea-to-Summit Ascent Ac II is a 15-degree down men’s sleeping bag that can be used for camping and backpacking. It has a versatile zipper system that lets it be configured in a wide variety of ways to fit different sleeping styles and temperature needs. For example, you can use it as a mummy bag or open it up like a quilt, it can be zipped together with the female version to create a double bag or folded-down in front like a blanket. There’s even a zippered foot box that lets you vent your feet if they’re too warm.

Specs at a Glance

  • Temperature rating: 15F (comfort range 15-65F degrees)
  • Gender: Unisex (men’s)
  • Weight: 2 lbs 6.8 oz
  • Draft Collar: Yes
  • Draft Tube: Yes
  • Footbox Zipper: Yes
  • Insulation: Ultra-Dry Duck Down 750+ fill power
  • RDS-Certified: Yes
  • Compression sack: included
  • Storage sack: included
  • Shell Fabric: 20d
  • Length: 6 feet, (6′ 6″ long size also available)
  • Dimensions: (Shoulder/Hip Feet) 61″/57″/48″
  • Recommended stuff sack size: 10L

Design

The Sea-to-Summit Ascent Ac II is designed to span a wide range of sleeping styles and temperatures, from side sleepers and back sleepers to solo sleepers and couples, including people who want a more quilt-like sleep experience sometimes or that of a mummy bag. If you’re looking for one sleeping bag that could serve multiple people in your family, the Ascent Ac II would be a good candidate.

The zippered footbox lets you vent the bag of your feet are too warm.
The zippered footbox lets you vent the bag of your feet are too warm.

The Ascent Ac II has a rectangular shape rather than a tapered mummy with a shallow mummy hood on top. The down is distributed on both the front and back of the bag, with vertical baffles over the chest and horizontal ones from the knees down to keep the down from migrating and creating cold spots.

If you unzip the left and righthand zippers, you can fold down the top of the sleeping bag like a blanket
If you unzip the left and righthand zippers, you can fold down the top of the sleeping bag like a blanket

The Ascent Ac II comes with all of the normal features you’d expect on a quality down sleeping bag including down-filled draft tubes behind the zippers, a down-filled draft collar that wraps around the front of your chest around the back of your shoulders and neck, and a mummy hood that can be controlled independently of the draft collar. The fabric along all of the zippers is reinforced with a stiffer to prevent snags, which can lead to tears in the fabric, which is a feature you really only find on premium sleeping bags.

Vertical baffles over the chest and horizontal ones over the legs prevent down shift and cold spots
Vertical baffles over the chest and horizontal ones over the legs prevent downshift and cold spots

But the key to Ascent AC’s chameleon-like versatility lies in its zippers:  all three of them. There’s a zippered footbox that you can open to cool off if your feet are two warm, a full-length right-hand zipper, and a 1/2 length left zipper. All three are two-way zippers so you open them partially for venting or unzip them all the way.

Here are some ways that you can use the side zippers, to give you a flavor of what’s possible.

  • If you unzip the right and left-hand side, you can fold the top of the sleeping bag over like you would a blanket.
  • If you need to reach a headlamp at night, you can open the left-hand zipper from the bottom from inside the bag, and snake out a hand to get your headlamp without having to open the front of the bag and expose your chest or neck to the cold.
  • You can unzip the full-length zipper and the footbox zipper, to fully open the sleeping bag and use it as a blanket or quilt, for two. This is great for watching meteor showers with your best friend.
  • You can zip together the Ascent Ac II with a Sea-to-Summit Altitude Journey or Venture sleeping bag to form a double sleeping bag for two.
Snaps at the size help take pressure off the YKK zippers
Snaps at the size help take pressure off the YKK zippers, ensuring better longevity.

While the Ascent Ac II is a mummy bag, it’s still easy to sleep on your side if you don’t cinch down the hood and wear a warm hat instead. The hood can also be used to hold a pillow in place and prevent it from wandering away.

The Ascent Ac II comes with a storage bag and a compression sack
The Ascent Ac II comes with a storage bag and a compression sack

Finally, the Ascent Ac II comes with its own compression sack so you can save the expense of buying a new one. Uncompressed, it will stuff down into a 10L waterproof stuff sack but it is a tight fit and may be more difficult to fit into the bottom of your backpack.

Recommendation

The Sea-to-Summit Ascent Ac II is an innovative down sleeping bag that emphasizes comfort and versatility over ultralight weight. If you’re looking for a warm and roomy sleeping bag that can be used across a wide range of temperatures, the unique zipper system used by this sleeping bag provides an unprecedented level of flexibility. While not for everyone, the Ascent Ac II is a great find if you want one bag that can do it all without compromising on fit or features.

Disclosure: The author received a sample bag from Sea-to-Summit for this review.

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4 comments

  1. Anyone know the stuff size or compression size in inches?

  2. Hmmm, with 750 down, and the extra zippers and snaps, then how do they get it rated for 15degrees and 2.3 lbs. Seems like it should either be heavier, or not as warm.

    • Bag design matters. You can’t fake these sleeping bag ratings. They’re done by independent testing labs using a standard methodology.

  3. My lady uses one of these and considers this the best purchase we’ve made for our camping trips. Huge fan of the zipper setup.

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