Can I zip two Sea to Summit sleeping bags together?

Zipping two compatible sleeping bags together forms a warm, cozy, comfortable sleep environment for two people. This is a far more flexible option than a double sleeping bag (which explains why there are so few double sleeping bags on the market).
BUT not all sleeping bags can be zipped together. Below you will find a table which details which Sea to Summit bags can be coupled – there are notes at the bottom which provide further clarification about which side zipper is referred to in the table (and give some caution about zipping non-Sea to Summit sleeping bags to Sea to Summit models).
Current Sleeping Bags
Model | Year | Zip Side/Type | Zip Compatibility |
Alpine | 2024 | Left #5 | None |
Spark 45°F | 2024 | Left #5 half zip | None |
Spark 30°F | 2024 | Left #5 half zip | None |
Spark 15°F | 2024 | Left #5 full zip |
Women's Spark 15°F Any STS bag w/ a Right #5 full zip |
Spark 0°F | 2024 | Left #5 full zip |
Women's Spark 15°F Any STS bag w/ a Right #5 full zip |
Women’s Spark 45°F | 2024 | Right #5 half zip | None |
Women’s Spark 30°F | 2024 | Right #5 half zip | None |
Women’s Spark 15°F | 2024 | Right #5 full zip | Any STS bag w/ a Left #5 full zip |
Spark Pro | 2024 | Left #5 full zip | Any STS bag w/ a Right #5 full zip |
Ascent | 2024 | Left #5 full zip | Any STS bag with a Right full #5 zip |
Women's Ascent | 2024 | Right #5 full zip | Any STS bag with a Left #5 full zip |
Trek | 2024 | Left #5 full zip | Any STS bag with a Right #5 full zip |
Women's Trek | 2024 | Right #5 full zip | Any STS bag with a Left #5 full zip |
Basecamp | 2024 | Left and Right #5 full zip |
Basecamp Any STS bag with a Right full #5 zip |
Traveller | 2024 | Left #5 full zip | 2024 Traveller w/ the same zip length |
Hamelin | 2025 | Left #5 wraparound zip | None |
Women’s Hamelin | 2025 | Right #5 wraparound zip | None |
Boab | 2025 | Left #5 wraparound zip | None |
Traverse TV | 2019-2024 | Left #5 full zip | Any STS bag w/ a Right #5 zip |
Venture | 2019 - 2024 | Right #5 full zip | Any STS bag with a Left #5 zip |
Trailhead | 2019-2024 | Left #5 wraparound zip | None |
Quest | 2019 - 2024 | Right #5 wraparound zip | None |
Past Sleeping Bags
Model | Year | Zip Side/Type | Zip Compatibility |
Alpine | 2010-2023 | Left #5 full zip | None |
Spark I | 2015 – 2023 | Left #3 half zip | None |
Spark II | 2017 - 2023 | Left #3 half zip | None |
Spark III | 2017 – 2018 | Left #3 full zip | None |
Spark III | 2019 - 2022 | Left #5 full zip | Any STS bag with a Right #5 full zip |
Spark IV | 2019 - 2022 | Left #3 full zip | None |
Spark IV | 2023 | Left # 5 full zip | Any STS bag with a Right #5 full zip |
Flame I | 2015 – 2023 | Right #3 half zip | None |
Flame II | 2017 - 2023 | Right #3 half zip | None |
Flame III | 2017 – 2018 | Right #3 full zip | None |
Flame III | 2019 - 2022 | Right #3 half zip | None |
Flame III | 2023 | Right #5 half zip | Any STS bag with a Left #5 full zip |
Flame IV | 2019 - 2022 | Right #3 full zip | None |
Flame IV | 2023 | Right #5 full zip | Any STS bag with a Left #5 full zip |
Ascent | 2019 – 2023 | Left # 5 full zip | Any STS bag with a Right #5 full zip |
Altitude | 2019-2023 | Right #5 full zip | Any STS bag with a Left #5 full zip |
Trek | 2010-2023 | Left #5 full zip | Any STS bag with a Right #5 full zip |
Women's Trek | 2016-2018 | Right #5 full zip | Any STS bag with a Left #5 full zip |
Journey | 2019-2023 | Right #5 full zip | Any STS bag with a Left #5 full zip |
Traverse XT | 2010-2016 | Left #5 full zip | Any STS bag with a Right #5 full zip |
Micro | 2010-2016 | Left or right #3 full zip | Only 2010-2016 Micro with opposite zipper side |
Micro | 2017 - 2018 | Left or right #5 full zip | Any STS bag with opposite zipper side #5 full zip |
Traveller | 2016 – 2023 | Left #3 full zip | Another 2016 – 2023 Traveller of the same length |
Talus | 2012-2018 | Left #5 full zip | Any STS bag with a Right #5 full zip |
Latitude | 2016-2018 | Left #5 full zip | Any STS bag with a Right #5 full zip |
Women's Talus | 2016-2018 | Right #5 full zip | Any STS bag with a Left #5 full zip |
Women's Latitude | 2016-2018 | Right #5 full zip | Any STS bag with a Left #5 full zip |
Amplitude | 2019-2022 | left and right #5 full zip | Another Amplitude/Basecamp or any STS bag with a #5 full zip |
Note - in the above table, the zipper referred to is the main side zipper. Some bags also have a footbox zipper; some have a secondary short side zipper. The zipper used to couple two sleeping bag together is always the main side zipper.
To be compatible, bags must both have a full zipper. Sleeping bags with a wraparound or half zipper cannot be zipped to other bags.
The zipper descriptions relate to Sea to Summit sleeping bags. A sleeping bag from another brand may zip together with a Sea to Summit bag provided the zipper is the same size and has the same teeth oriented in the same way facing inwards. In case of doubt when trying to couple two bags, do not force a zipper slider - damage can result to the zipper slider or zipper track.