For milder nights when a compact down bag and room to move matter. The Circuit combines a roomy semi-tapered rectangular shape with 650+ fill power Ultra-Dry duck down. Open the wraparound zip to vent your feet or lay the bag flat as a quilt.
Three reasons to choose Circuit
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Space to sleep on your side: a roomy shape and soft brushed lining.
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Warmth without unnecessary bulk: 650+ fill power RDS-certified Ultra-Dry duck down.
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Vent or open flat: the wraparound zip opens the footbox and converts the bag to a quilt.
Choose your size
−1°C Regular and Long specifications
| Specification |
Regular |
Long |
| Recommended sleeper height |
Up to 185 cm |
Up to 198 cm |
| Bag weight |
820 g |
910 g |
| Packed weight |
950 g |
1040 g |
| Down fill weight |
411 g |
469 g |
| Compressed volume |
5.4 L |
6 L |
| Bag length × width |
207 × 72.5 cm |
222 × 77.5 cm |
| Packed dimensions |
41 × 22.5 × 15.5 cm |
41 × 22.5 × 15.5 cm |
Choose by recommended sleeper height. Bag length is the overall length. Manufacturer weights and packed measurements are average figures.
Choose your warmth
ISO comfort: +2°C. ISO lower limit: −1°C. The model name uses the lower limit. Start with comfort if you sleep cold, and allow a margin for the forecast, your mat and clothing.
| Circuit model |
Comfort / limit |
Regular weight / volume |
| −1°C (this model) |
+2°C / −1°C |
820 g / 5.4 L |
| −9°C |
−5°C / −9°C |
1160 g / 9.7 L |
Construction and features
- 650+ fill power duck down with RDS certification and a non-PFAS Ultra-Dry treatment.
- 20D recycled polyester shell and lining, with a soft brushed inner feel.
- Hybrid box baffles help hold the down in place.
- Left-hand full-length YKK #5 wraparound zip with an anti-snag plough.
- Shaped collar and down-filled draft tubes help reduce heat loss.
- Internal zipped pocket for small essentials.
- Dark Blue colour.
What’s included
- Sea to Summit Circuit Down Sleeping Bag −1°C
- Compression sack
- Storage cell
Frequently asked questions
Does −1°C mean I will be comfortable at that temperature?
The model name uses the ISO lower limit: −1°C. Its ISO comfort rating is +2°C. Start with comfort if you sleep cold, and allow a margin for the nights you expect. Ratings are laboratory comparisons, not a guarantee for every sleeper. An insulated mat, shelter and clothing also affect warmth.
Should I choose Regular or Long?
Regular is recommended for sleepers up to 185 cm. Long is recommended up to 198 cm and is also 5 cm wider. These are recommended sleeper heights; the 207 cm and 222 cm figures are the overall bag lengths. Choose a fit that leaves room at your feet without pressing the insulation flat.
How is the −1°C different from the −9°C?
Both have the same roomy shape, 650+ fill power down and wraparound zip. The −1°C has a +2°C comfort rating and weighs 820 g in Regular. The −9°C has a −5°C comfort rating and weighs 1160 g in Regular. Choose −9°C for the colder comfort rating, allowing for its greater weight and packed volume.
Can it open flat or zip to another sleeping bag?
It opens fully flat as a quilt. You can also open the footbox while keeping the upper section zipped. Circuit bags cannot zip together or couple with other Sea to Summit bags; this model has a left-hand wraparound zip.
Is it waterproof?
No. Ultra-Dry Down and the water-repellent shell help manage moisture, but the bag is not waterproof. Keep it protected from rain and water in your pack and use suitable shelter.
Is there a women’s version?
Circuit is a unisex range. Use the comfort rating as your starting point if you sleep cold: +2°C for this model. Choose Regular or Long by your height and the room you need.
What is included, and how should I store it?
The sleeping bag includes a compression sack for transport and a storage cell for keeping it loose between trips. Air it after use, let it dry completely and store it uncompressed. Follow Sea to Summit’s care instructions for cleaning.
