The Sea to Summit Spark SpIV Down Sleeping Bag is currently exclusively available in the UK here at Ultralight Outdoor Gear.

UOG TOP PICK - Sea to Summit Spark Series Sleeping Bags - Best Warmth to Weight ratio - We've singled out Sea to Summits Spark sleeping bags as one of our recommendations because its a minimalist in the true sense of the word, it only includes a few key features but delivers exceptional warmth given its very low weight.

Sea to Summit says:

Ultra-light and technical, our Spark Series bags are designed to keep you as warm as possible while minimising packed weight and size.

The Spark Series spans everything from an ultralight liner to an expedition weight mid-winter bag. While the end usage is very different, they reflect a design ethos of matching weather conditions to the lightest bag possible.

The secret to the impressive performance is a combination of premium materials and careful design. The RDS 850+ Loft premium goose down, light-gauge #3 YKK zip and high performance 10D Nylon shell and 7D lining fabrics, set the stage for a superior performance. These materials are combined with a contoured mummy design for efficient insulation, and that mummy design is then tweaked for each model to best fit the use scenario.

Our 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. All Sea to Summit Down Sleeping Bags use Responsible Down Standard (RDS) certified down. The Ultra-Dry Down protection also makes the Spark an impressive hard-alpine or adventure racing bag, where every gram is counted and down has never been a viable option.

Sea to Summit's Spark SpIV Down Sleeping Bag is a true minimalist expedition bag that uses the lightest materials and highest quality, responsibly sourced down to deliver an exceptionally high warmth to weight ratio, when compared to other similarly rated bags.

The Spark IV bag features vertical baffles on the chest area to minimise movement of down, optimising insulation where you need it most. The bag uses box wall construction throughout which reduces the cold spots you get with sewn construction. The full zip with 2 sliders allows good venting options if conditions are too warm. There is a small insulating zip baffle and further draft collars around the head to limit heat loss

The contoured mummy shape is roomy and the super thin and light outer fabrics means more care will be needed than with more heavy duty bags. The bag compress's down to a very small size.

- Reviewed by Ultralight Outdoor Gear

Read reviews here:

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UOG TOP PICK - Sea to Summit Spark Series Sleeping Bags - Best Warmth to Weight ratio - We've singled out Sea to Summits Spark sleeping bags as one of our recommendations because its a minimalist in the true sense of the word, it only includes a few key features but delivers exceptional warmth given its very low weight.

Help and advice:

Ultralight 7D and 10D fabrics for minimal weight and packed size
RDS 850+ Loft Premium Goose ULTRA-DRY Down for maximum insulation value
Contoured mummy shape for comfort and efficient insulation
Vertical chest baffles prevent down migration and cold spots
This bag is not designed to pair with another
Uses a full box baffle construction to accommodate extra down and reduce cold spots
Expedition mummy bag sizing provides extra space for layered clothing or extra wriggle room
Vertical baffles on chest optimises positions of down to prevent it from moving during use
Full side zip with two sliders provides easy access and extra ventilation options
Zipper draft tube, hood and front neck draft collar to prevent warmth being lost when it's needed

Temperature Rating

EN13537:2012 Comfort: -8°C / 18°F
EN13537:2012 Comfort Limit: -15°C / 5°F
EN13537:2012 Extreme: -36°C / -33°F

Regular Specs

Weight: 856g (excludes storage bags)
Fill weight: 620g
Fits up to: 6 ft / 183 cm
Internal Width Shoulder: 155cm / 61 in
Internal Width Waist: 135cm / 53 in
Internal Width Feet: 94cm / 37 in

Materials

Insulation: RDS 850+ Loft Premium Goose ULTRA-DRY Down
Shell: Ultralight 10D Nylon Shell
Zipper: Left-side #3 YKK zipper
Comes with: Ultra-Sil™ compression bag and storage cell

EN13537:2012 - Look for the 2012 label for the most accurate rating; In 2012 the EN system of testing sleeping bags was re-vamped - the new testing procedures are more rigorous, producing more consistent results than previous tests. 2012 results tend to rate sleeping bags as poorer performing by a few degrees when compared to previous test results, even though the sleeping bag may be identical, or even better.

Showing our 2 Sea to Summit Spark SpIV Down Sleeping Bag reviews with an average rating of Good. Would you like to write a review?

Review Summary - 3 out of 5 based on 2 ratings.

December 20, 2021 | Matt Wells

A Compromise

This is an interesting bag but not without its faults. It's well made and much tougher than it looks, It's warm but only when it's fully zipped up and the hood is cinched in. It's comparatively light but I wouldn't rely on it to anywhere near -15c. The zip is the worst thing about it. It really is bad but as long as you coax it gently, rather than tug at it, it does the job. The Hydrophobic down is brilliant and overall it works - I just wouldn't buy it again.

Ultralight Outdoor Gear Limited

October 6, 2021 | Richard Moulding

Very warm but much too fragile

There's no doubt that that this is one very warm bag, especially considering its low weight. However, the zip is dreadful. It actually trapped me inside for 10 panicky minutes. It sticks on nearly every unzipping. It's also a very fragile shell. I snagged the lining with the zip and with just a normal pull to free it, it ripped a hole that leaked down, requiring fixing with Tenacious tape in the middle of the night. I'd only recommend it if weight and warmth is you only criteria. If any sense of durability is a factor for you (and it should be) then look elsewhere.

Ultralight Outdoor Gear Limited