Sea to Summit Hamelin -9C/15F Synthetic Sleeping Bag

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Versatile, roomy, and reliably warm.

Sea to Summit says: 

A backpack-capable sleeping bag with a higher level of comfort than traditional mummy bags. For a few extra grams and larger packed size, Hamelin brings the benefits of synthetic insulation in wet/sandy environments. Designed for comfort and
performance, the relaxed mummy fit offers plenty of room to move. The full-length side zipper extends throughout the foot box, along with a half-length zipper on the opposite side it provides ventilation and versatility.

Our Verdict

The Sea to Summit Hamelin -9C blends reliable performance with a relaxed fit that feels less restrictive than most mummy-style designs. The contoured  fit allows for more natural movement without creating excess dead space, and the anatomically shaped footbox helps maintain warmth where it’s needed most.

The bag is rated to a lower limit of -9°C, and it performs well for most winter trips. The double-zip system, full-length on one side, half-length on the other, allows for excellent venting options or even converting the bag into a quilt on warmer nights.

At 1626g (Regular), it’s on the heavier side. Still, the durable 50D shell, smooth-running zip with plough, and thoughtful extras like the draft collar and pillow-compatible hood make it feel like a fully considered system rather than a pared-back option.

If you’re looking for comfort and resilience across a range of conditions, and don’t mind a bit of extra bulk, the Hamelin is a strong all-rounder.

– Reviewed by Ultralight Outdoor Gear

Features

• Bluesign approved, 20D recycled polyester shell with PFC-free  WR. 20D bluesign-approved recycled polyester liner.
• 100% RCS-certified, postconsumer, recycled, multidenier  synthetic insulation.
• Free Flow zipper system and relaxed mummy fit for comfort and performance across multiple seasons, varying weather and challenging environments.

Specifications

Regular

• Weight: 1626g
• Comfort: -3°C | 27°F
• Lower Limit:-9°C | 15°F
• Max User Height: 185cm 
• Fill weight: 1210g
• Fit: Contour – Women’s-specific relaxed mummy

Long

• Weight: 1915g
• Comfort: -3°C | 27°F
• Lower Limit:-9°C | 15°F
• Max User Height: 185cm 
• Fill weight: 1375g
• Fit: Contour – Women’s-specific relaxed mummy

Material & Construction

• Fabric – Bluesign approved, 50D recycled polyester shell, PFC-free DWR. 50D bluesign- approved recycled polyester liner.
• Insulation – 100% RCS certified, postconsumer recycled, multidenier polyester. Offset insulation avoids cold spots
• Zip – #5 Side zipper continues through footbox. Zipper plough, double sliders. #5 half length zipper on opposite side.
• Neck Draft Coller – Front draft collar
• Foot Box – Generous, anatomically shaped footbox avoids cold spots
• Draft Tube – Yes
• Pillow Integration – Hood accommodates Regular Aeros Pillow

Help & advice:

• The Ultimate Guide to Lightweight Sleeping Bags
• Time-Saver Guide to Choosing a Sleeping Bag
• Sea to Summit Sleeping Bag & Quilt Guide
• Sea to Summit Sleeping Mat Guide
• About Sea to Summit