Sea to Summit has been making top-quality outdoor gear since their debut in 1990. Founded in Perth, Western Australia, it all started in 1983 when adventurer Roland Tyson began making his own gear as lightweight outdoor products were hard to find. In 1990, Australian mountaineer, Tim Macartney-Snape asked Mr. Tyson to make gear for his Mount Everest climb. The expedition and gear were a success, and the Sea to Summit brand was born. 

The Sea to Summit Spark Ultralight sleeping bag is extremely comfortable, durable, suitable for temperatures that drop down 40°F (5°C) and super light, weighing only 340g. The ULTRA-DRY Down is water repellent, and made with Responsible Down Standard (RDS) certified goose down. The sleeping bag is a contoured mummy shape for comfort and efficient insulation.

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  • Ultralight at 340g
  • Water-resistant
  • Premium goose down
  • Contoured mummy design for comfort
  • Design prevents down from migrating


  • Price
  • Only one colour
  • One buyer said “not much room in foot area”
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Things to Consider Before Buying a Sleeping Bag

  • Season: Decide what season you need the sleeping bag for
  • Temperature rating: Find out the temperature rating you need it for such as 5°F (-15°C), 32°F (0°C), or 60°F (15°C)
  • Size and shape: Decide on the sleeping bag size and shape, like rectangle, tapered, or mummy style bag
  • Down vs. Synthetic: Look for what type of material is the sleeping bag made of, for example down or synthetic
  • Waterproof: Consider getting a waterproof, breathable shell layer. This is to prevent snow, rain and condensation from soaking through 
  • Hood: If you’re camping in very cold weather, hoods are essential
  • Zippers: If you’re looking for an expedition sleeping bag, a small zipper is preferable. In warmer climates, the zipper will often open up like a blanket
  • Pockets: Look for internal pockets rather than external pockets, so you don’t have to get out of the sleeping bag
  • Foot box: Remember your feet are likely to be at the end of the tent, often touching the tent. Look for waterproof materials for the foot box.

Why You Should Consider the Sea to Summit Spark I Ultralight

Weight and Packability

There’s a reason why the Sea to Summit Spark is called an Ultralight sleeping bag. At just 340g, it’s about the same weight as a can of beer. If you’re on an expedition or overnight hike, every gram counts, especially when you’re carrying a tent, food, and cooking utensils. One of the other benefits is that the Spark sleeping bag features ultralight 7D and 10D fabrics for minimal weight and packed size.

The packability advantage makes the Spark sleeping bag smaller than the average water bottle. After taking the Ultralight bag on a recent camping trip with the family, it only took a couple of minutes to pack the sleeping bag up. Depending on how hard you pull the straps, the approximate packed sleeping bag size is about 18cm high x 15cm wide. 


The lovely goose down is like sleeping on a bed of clouds. It’s so comfortable it makes you not want to get up, and skip both breakfast and your morning hike. The contoured mummy shape has been designed for comfort reasons too.

Forget about using a sweater as a pillow. To add another level of comfort, you need to jump on the Sea to Summit Aeros Down Pillow train. With the comfort and warmth of premium down, it’s among the lightest fully-featured down pillows on the market. Weighing only 70g, the pillow compacts down to half the size of the average water bottle when packing it up.

Aeros Down Pillow buyer Francois D. said, “Very comfortable and very compact pillow.

Pillow with a good thickness which does not crush when sleeping unlike memory foam pillows. The small layer of down adds to the comfort and provides a nice warmth. It takes up very little space when stored – perfect for hiking. I recommend taking the large model if you want a little more surface area because the regular is really small. The thickness is the same regardless of whether it is wide or regular. Make minus 1 on the dimensions to get a good idea of the actual size when inflated.”


The Sea to Summit Spark is a summer sleeping bag and is suitable for temperatures dropping down to 40°F (5°C). RDS 850+ Loft Premium Goose Down is for maximum insulation value. Sea to Summit said, “850+ Fill Power indicates that one ounce (30g) of down will re-expand to over 850 cubic inches after compression. Higher loft means that less down can be used to achieve the same temperature rating – important for performance sleeping bags. The loft and down quality/composition are independently tested by the International Down and Feather Laboratory (IDFL) – a copy of the certification is supplied with every Sea to Summit sleeping bag.”

The sewn-through vertical baffles on the chest optimize the position of goose down to prevent it from moving during use. 

Weather Resistance

The ULTRA-DRY Down water-repellent treatment protects the down from external moisture and condensation from the inside of the bag, virtually eliminating the negative effects moisture has on down.

Design and features

The Spark features an ultralight liner and has been designed to match expedition weather conditions. Although the design of the Spark is a contoured mummy shape, there’s extra room for both the shoulders and hips while still maintaining insulation efficiency.

Although there’s not a lot of extra features, the most appealing part of Spark Ultralight is its weight and packed size.

Sea to Summit sleeping bag next to its compressed size and a water bottle comparison

What Buyers Think

Exceptionally light and packable. I did not use a liner and found it slightly on the warm side, usually a 40°F (5°C) bag is comfortable at 50 - 60°F (12 - 15°C), I find this bag is a bit too warm when used at 60°F (15°C).” - Mark L.

“My favorite feature about the Spark, besides the weight, is the almost see-through shell. This allows me to visually ensure the down is balanced out before laying down for the evening.” - Scott Bideau


Q: How warm is the Spark sleeping bag?

A: The Spark Ultralight sleeping bag will keep you warm when it drops down to 40°F (5°C) at night. Due to the design, high zippers, ULTRA-DRY Down water-repellent and RDS 850+ Loft Premium Goose Down you’ll feel as warm as a Caribbean summer. Just ask buyer Mark L.

Q: Is there a warmer version of the Sea to Summit Spark I sleeping bag?

A: Yes, there’s the Spark Sp II version that will keep you warm in 28°F (-2°C) temperatures, and there’s also the Spark SP III version that has a 18°F (-8°C) temperature rating for even colder nights.

Spark Sp II Ultralight buyer Mario M said, “For the long hike, it is an ideal companion. And despite its minimalist appearance, it’s down (which seems to be insufficient) is actually extremely comfortable and warm. Really, it's a great discovery and it meets the description exactly given in detail on Altitude Sports.”

Q: Do I need to be really strong to pack it like a ball?

A: Some cheap sleeping bags take a long time to pack, but with the Spark Ultralight, your strength only needs to be the equivalent of a 12-13-year-old. Take advantage of the straps and simply pull, pull, and pull! You’ll be able to pack the sleeping bag within three minutes.

Sac de couchage Sea to Summit Spark I ouvert


There’s nothing worse than feeling cold in the middle of the night when camping, even with spooning your partner or accidentally spooning your friend. To avoid awkward chats the next morning, you need a warm sleeping bag like the Sea to Summit Spark I Ultralight. We understand its not cheap, but when going on an expedition trek or overnight hike, remember every gram counts. At only 340g and when you’re averaging 10-25 km each day, you’ll need every big of energy to reach your goal and campsite.