Sea to Summit Spark SpIII
Best ultralight sleeping bag for minimalist backpackers and alpine adventurers.
This is the gold standard for anyone who counts every gram without sacrificing warmth. By using premium high-loft down and a minimalist shell, it achieves an incredible warmth-to-weight ratio. You sacrifice a bit of interior wiggle room for that extreme packability, but for serious alpine pursuits, it is a necessary trade-off.
$999.00
at
Sea to Summit
Who it's for
- Ultralight backpackers prioritizing maximum warmth at minimal weight
- Thru-hikers needing to maximize limited pack space
- Backpackers venturing into humid or unpredictable climates
Who should skip it
- Budget-conscious hikers seeking value over pure performance
- Adventurers who are rough on their gear
- Side sleepers who need extra room to move
Performance breakdown
Warmth-to-Weight Ratio
The 850-fill down delivers exceptional thermal efficiency for its minimal weight.
Packability
Compresses down to palm-sized dimensions for effortless storage in tight packs.
Moisture Resistance
Ultra-Dry Down treatment reliably guards against condensation and damp trail conditions.
Construction Quality
Box baffle design and premium materials ensure long-term durability and loft.
Ergonomic Comfort
The mummy shape balances efficient heat retention with surprising roominess.
Weather Versatility
Excels across three seasons, from alpine expeditions to chilly hut trips.
Key Specs
Material
10D nylon, DWR coating, 15D nylon
Insulation
Ultra-Dry Down 850+
Shape
mummy
Zipper
left
Max User Height
6 ft (regular), 6 ft 7 in (long)
Shoulder Circumference
57 in (regular), 60 in (long)
Hip Circumference
50 in (regular), 52 in (long)
Foot Circumference
35 in (regular), 37 in (long)
Bag Length
6 ft (regular), 6 ft 7 in (long)
Pockets
none
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