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Sea-to-Summit Spark Pro Down 30 Sleeping Bag Review

Sea-to-Summit Spark Down Sleeping Bag Review

The Sea-to-Summit Spark Pro Down 30 Sleeping Bag is a top-of-the-line ultralight 950 fill-power down mummy sleeping bag with premium features, including a draft collar, zippered footbox, and dual side zippers. The shell and liner are made with lightweight 10D nylon fabric with box baffling over the torso and sewn-through construction over the legs. Like many of Sea-to-Summit’s sleeping bags, the Spark Pro has two side zippers, one long and one short, so you can vent the bag on both sides or stick your arms out while still wearing the hood. However, the Spark Pro has one fatal flaw, in our opinion: a badly performing zipper on the short side that will leave you cold and shivering at night when it comes off its tracks in the dark.

  • Type: Mummy sleeping bag
  • Temperature Rating: 30F Lower Limit; 37F Comfort
  • Insulation: 950 fill power down with non-PFC waterproofing
  • Weight: 21.8 oz
  • Fill Weight: 10.9 oz
  • Draft Collar: Yes
  • Construction: Box baffling in torso, sewn-thru over legs
  • Fabric: 10D nylon shell and liner
  • Compressed volume: 5.3L
  • Compression Sack: Included
  • Pros: 950 fill power waterproof down, dual side zippers, zippered footbox
  • Cons:  Poorly designed side zipper

The Sea-to-Summit Spark Pro Down 30-degree sleeping bag has awesome specs on paper. Its 950-fill power waterproof down is top-notch and provides excellent warmth and compressibility. The hood is comfortable without being claustrophobic, even if you’re a side sleeper, and you can even fold it down underneath you if you want to use the back more like a quilt in warmer weather. The bag’s three zippers, including a ventable footbox and two side zippers, allow you to regulate your temperature in numerous ways across a wider temperature range. All three zippers are well insulated with draft tubes, which cover the zippers inside the bag and prevent cold air from leaking in and chilling you.

The sleeping bag has a zippered footbox which can be vented.
The sleeping bag has a zippered footbox that can be vented.

In addition to the footbox zipper, the Spark Pro has two side zippers, one about 3/4 of the way down the left side and another 1/3-length zipper on the right. When both are unzipped, you can stick your arms out the sides while still wearing the hood, which is great on cold mornings when you want to cook food but stay inside your bag to remain warm (There are snaps at the top of each zipper to keep the sides from falling down.) We also like the shorter shoulder zipper as a ventilation option when you want to moderate your torso’s temperature.

The longer of the two zippers works perfectly. Sea-to-Summit uses a special two-way YKK snag-free zipper, and the fabric sides are taped to prevent snagging. The problem is the short zipper on the other side of the bag. While it is also a two-way zipper, there isn’t a stopper to prevent the sliders from coming off when you unzip the zipper (specifically when you pull the top slider down to open the zipper). We can’t tell whether this is a manufacturing defect or by design. But in either case, it means that you can’t reliably close this zipper once the sliders come off without having to reseat them…which is devilishly difficult to do from inside the bag.

The Spark Pro Down Sleeping bag has two upper zippers
The Spark Pro Down Sleeping bag has two upper zippers, so you can extend your arms while still wearing the hood or vent the bag from either side.

Imagine the following scenario: You’re too warm, so you open the short zipper all the way, and the sliders, unknown to you because it’s dark and you’re half unconscious, fall off the zipper. Several hours later, you go to close the zipper because your body has cooled, nothing happens, and you’re stuck with a gaping hole that’s leaking cold air into your bag. So you get out your headlamp, get out of the bag, fiddle with the sliders to reseat them, close the zipper again, get back into your bag, and try to get back to sleep…fuming how you’re going to return this sleeping bag to REI or some other retailer because it sucks.

The sliders come off when you open the short zipper. The sliders are also small and difficult to reseat.
The sliders come off when you open the short zipper. The sliders are also small and difficult to reseat.


While we can understand Sea-to-Summit’s desire to create an Uber sleeping bag with temperature regulation features for all situations, we question whether putting three zippers on one sleeping bag is just asking for trouble. Zippers are often the biggest point of failure in any piece of outdoor clothing or gear. In any event, if you put zippers on a sleeping bag, you want them to work with a minimum of hassle or maintenance for the lifetime of the sleeping bag. We can’t recommend the Spark Pro Down 30 sleeping bag due to the issues we encountered with the short zipper. It’s too bad because this would be an awesome sleeping bag otherwise.

Shop at REI


Disclosure: Sea-to-Summit donated a sleeping bag for review.

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One comment

  1. Have to love your integrity! You say it as you see it.

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