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A roomy, adaptable down bag with a much simpler approach to ventilation.
Sea to Summit says:
Adapt to any Adventure.
Climate Control - Tapered rectangular shape and wrap-around zipper let the Circuit adapt to changing conditions-open to a quilt in warm conditions or zip closed when the temp dips towards freezing. Easy climate control with antisnag zipper plough for footbox venting.
Light and Packable - Ultralight 20D fabric and 650+ fill Ultra-Dry down make a bag light enough for the backcountry yet perfect for camping and travel, Included compression sack for easy packability.
Comfort and Warmth - Roomy shape, light and soft touch fabrics make the Circuit a comfortable bag to sleep in while full down draft tubes coupled with a hybrid box baffle construction keep the down securely in place to ensure warmth to its tested ISO temperature rating.
Lower Impact Materials - 100% RDS Certified down, 100% Non-PFAS materials and 100% recycled, bluesign APPROVED fabrics.
Our Verdict
roomy rectangular design. Its tapered shape gives you plenty of space to move without creating the large areas of dead space that can make rectangular bags harder to warm.
The wraparound zip really works for me. Two zip pulls let you open the footbox for ventilation, unzip the bag from the side or lay it completely flat as a large quilt. I find this arrangement much easier to manage than designs with separate side and footbox zips, particularly when trying to close everything again during the night.
The 650+ fill-power down, draught collar and hybrid box-baffle construction should make it comfortable around its 2°C comfort rating, while the 20D recycled fabrics keep the Regular to 821g. It is available in Short, Regular and Long lengths, with the Regular fitting users up to 185cm.
It is not the lightest option for its temperature rating, but the extra room and straightforward temperature control make it well suited to general three-season backpacking and camping.
- Reviewed by Ultralight Outdoor Gear
Features
- Comfort in all conditions Opens flat for airflow on warm nights or zips closed to lock in warmth when temperatures drop
- Efficient packability Quality 650+ fillpower Ultra‑Dry Duck Down and lightweight fabrics allow the Circuit to pack down small into the supplied compression sack
- Room to move Soft touch liner and wider, thermally-efficient shape enhance warmth and comfort, no matter which position you sleep in
- Precise ventilation Wrap‑around zip lets you fully open the footbox for maximum venting and fine-tune airflow to regulate temperature
- Lightweight breathability Premium 20D fabric offers perfect next-to-skin comfort night after night after night
- Consistent insulation Hybrid box‑baffle construction prevents down migration, eliminating cold spots for even warmth
- Easy zipping YKK #5 coil zipper with anti‑snag plough ensures smooth, jam‑free operation in all conditions for hassle‑free use
- Draft protection Shaped collar and continuous down-filled draft tubes minimise heat loss and maximise retained warmth
- Verified warmth ISO 23537 certification confirms dependable insulation performance for rated temperatures
- Internal pocket Zippered pocket stores essentials like your phone or head torch securely while keeping them insulated from the cold
- Lower impact materials Constructed from bluesign APPROVED, 100% recycled fabrics designed to go the distance
Specifications
Short
- Weight: 768g
- Max User Height: 170cm | 5ft 7in
- Compression: 13L
- Temperature Comfort Limit: 2°C
- Temperature Lower Limit: -1°C
- Fill Power: 650+
Regular
- Weight: 821g
- Max User Height: 185cm | 6ft 1in
- Compression: 13L
- Temperature Comfort Limit: 2°C
- Temperature Lower Limit: -1°C
- Fill Power: 650+
Long
- Weight: 909g
- Max User Height: 198cm | 6ft 6in
- Compression: 13L
- Temperature Comfort Limit: 2°C
- Temperature Lower Limit: -1°C
- Fill Power: 650+
Material & Construction
- 100% recycled, bluesign APPROVED fabrics.
- Non-PFAS, RDS certified 650+ fillpower Ultra‑Dry Down
