30°F Down Backpacking Bags · 2026 Comparison
Sea to Summit Spark 30F vs REI Co-op Magma 30
Side-by-side published specs and honest spec-only analysis. No fabricated verdicts.
Quick Answer
On published specs, the Sea to Summit Spark 30F is 85 g lighter while both list the same MSRP ($349). For weight-conscious backpackers in the 30°f down backpacking bags category, that's the spec-sheet pick. The REI Co-op Magma 30 would need a fit, durability, or brand-loyalty reason to justify the choice.
The Specs Side by Side
Sleep SystemSea to Summit
Sea to Summit Spark 30F
- Price (MSRP)
- $349
- Weight
- 0.48 kg (482 g)
- Ultralight
- Yes
- Our rating
- specs only — no full review yet
Manufacturer description
30°F (-1°C) mummy, 850-fill down, ultralight 10D shell, ~0.48 kg.
Sleep SystemREI Co-op
REI Co-op Magma 30
- Price (MSRP)
- $349
- Weight
- 0.57 kg (567 g)
- Ultralight
- Yes
- Our rating
- specs only — no full review yet
Manufacturer description
850-fill down mummy, ISO ~34°F comfort / ~24°F limit, ~0.57 kg regular.
What the Numbers Say
- ▸Weight: Sea to Summit Spark 30F is the lighter of the two by 85 g (0.48 kg vs 0.57 kg). For thru-hiking and any pursuit where carry weight compounds across days, that delta matters.
- ▸Price: both list the same MSRP ($349) — the budget tiebreaker comes from sales, member rebates, or used-market availability.
- ▸Ultralight classification: both products are classified ultralight in their category — built for weight-conscious backpackers from the start.
- ▸Review coverage: neither has a full review yet. Specifications are taken from current manufacturer product pages.
Detailed Breakdown
Carry weight and packed size
On the published spec sheet, the Sea to Summit Spark 30F comes in at 482 grams against the 567 grams of the REI Co-op Magma 30. That 85-gram gap may sound trivial in isolation but compounds across multi-day trips — at 25 km a day for a week, you're carrying that delta for about 175 km of trail. The Sea to Summit Spark 30F's ultralight classification reflects the deliberate design choices that produce the saving: thinner fabrics, simpler architectures, or fewer secondary features.
Price and total cost of ownership
MSRP is identical ($349). The price question shifts to availability: retailer promotions, REI member rebates, or used-market listings often produce a meaningful gap between two products that look the same on the brand site. Check pricing weekly during shoulder seasons (late winter and late summer) when last year's models clear out.
Materials and durability
Material composition for both products comes from the manufacturer product pages and is not always reported in directly comparable units. The Sea to Summit Spark 30F carries the manufacturer's published spec only; the REI Co-op Magma 30 carries the manufacturer's published spec only. Without a full review of either, treat material and durability claims as starting points rather than verdicts. Reader reviews on REI or Amazon (filtered to verified purchases) often reveal failure modes that brand copy doesn't.
Features and ergonomics
Manufacturer feature descriptions: the Sea to Summit Spark 30F — 30°F (-1°C) mummy, 850-fill down, ultralight 10D shell, ~0.48 kg.. The REI Co-op Magma 30 — 850-fill down mummy, ISO ~34°F comfort / ~24°F limit, ~0.57 kg regular. Pay particular attention to fit, adjustability, and hand-feel — three dimensions that don't show on a spec sheet and that disproportionately determine whether you'll actually reach for the gear after the first trip.
Use-case fit
The 30°f down backpacking bags category covers a wide range of trip styles. For weight-counted thru-hikes, lean toward whichever is lighter on this page — every gram in your pack rides with you for thousands of kilometers. For weekend trips and base-camp days, weight matters less and durability, comfort, and feature count matter more — the heavier of the two on this page often makes more sense in those scenarios. For three-season generalist use, our recommendation: prioritize the product you can handle in a store or borrow from a friend, because neither has a full review on this site yet.
Brand support and availability
Sea to Summit and REI Co-op both produce 30°f down backpacking bags for the North American and EU markets. Availability varies: smaller cottage brands may require direct-from-manufacturer ordering with 2-6 week lead times, while bigger brands stock through REI, Backcountry, and large EU outdoor chains with same-week shipping. Before buying either, check the manufacturer's warranty terms (often 1, 2, or 10 years depending on brand culture) and the brand's reputation for honoring claims on minor failures versus catastrophic ones. Neither product has a full review on this site yet, so check owner reports for warranty experiences before buying.
Frequently Asked Questions
Which is lighter, the Sea to Summit Spark 30F or the REI Co-op Magma 30?
On published manufacturer specs, the Sea to Summit Spark 30F is the lighter of the two by 85 grams (0.48 kg vs 0.57 kg). For ultralight backpackers counting grams in the 30°f down backpacking bags category, that's a meaningful difference.
Which costs less, the Sea to Summit Spark 30F or the REI Co-op Magma 30?
Both products list the same MSRP ($349). Final price often depends on retailer promotions, REI member rebates, and seasonal sales rather than the sticker price.
Does this site have full reviews of both products?
Not yet. Neither the Sea to Summit Spark 30F nor the REI Co-op Magma 30 has a full review on this site yet. This comparison is built from published manufacturer specifications only, clearly labeled. Treat it as a shortlist starting point rather than a verdict.
Is the Sea to Summit Spark 30F ultralight by industry standards?
Yes. The Sea to Summit Spark 30F is classified ultralight in our database (0.48 kg, sub-threshold for its sleep system category). Ultralight 30°f down backpacking bags typically means built for thru-hikers and gram counters rather than three-season car-camping use.
Is the REI Co-op Magma 30 ultralight by industry standards?
Yes. The REI Co-op Magma 30 is classified ultralight in our database (0.57 kg, sub-threshold for its sleep system category). Built for thru-hikers and weight-conscious backpackers.
Is the price difference worth it?
There is no price difference at MSRP — both list at $349. The decision is purely about features, fit, and brand preference.
Where can I read the full review?
Neither product has a full review yet. The current page lists manufacturer-published specifications for both. We'll add full research-based reviews as published testing and owner feedback accumulate.
Bottom Line
Winner on weight: the Sea to Summit Spark 30F by 85 g (0.48 kg vs 0.57 kg). If your trip style punishes grams, that's the pick.
Winner on price: tied at $349 MSRP. Watch for promotions on either side.
Our overall lean: we don't have a strong overall lean because neither has a full review yet. Use this page as a shortlist tool, then read independent reviews on the brand sites, REI, and YouTube before deciding.