Sea to Summit Trek TkIII Sleeping Bag

-11°C Comfort Limit (EN13537:2012), 700g of 650+ Fill Power ULTRA-DRY Down (US Method)
Weighs 1176g (excluding stuff sack)
Code: SS19439
  • Now £319.99
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The Sea to Summit Trek TkIII sleeping bag is packed with useful features as well as 700g of responsibly sourced and dry treated down to keep you warm and toasty.

Sea to Summit says:

Traditional comfort and value, with an anything but traditional design approach, our Trek Series sleeping bags are what we grab for globe-trotting adventures on a budget.

Vertical baffles over the chest section ensure the down insulation cannot migrate or shift to the outside of the bag during sleep, creating cold spots. A side block baffle construction maintains the 60/40 fill ratio, keeping more down on the top of the bag for maximum insulation.

Lightweight fabrics reduce weight and packed bulk while the two-way #5 YKK full length side zip and separate foot zip, allows the bag to open out completely and double as a quilt. The foot zip is perfect for extra ventilation or to provide freedom of movement for your feet.

The 3D side-wall baffle ensures that down can loft to the very edge of the bag, maximising insulation, while the panelled hood draws in tight when needed of lies flat for use in warmer weather. The oversized zipper draft tube uses anti-snag materials to help prevent the zipper catching and the soft touch 20D lining fabric is highly breathable yet also down proof.

Completing the thoughtful design features of this classic down bag, we have included a large internal security pocket, perfect for keeping valuables close or batteries warm.

Sea to Summit's Trek TkIII Sleeping Bag is not amongst the lightest but is versatile and packed with useful features.

The standout feature is the full length 2 way zip and a further zip along the foot box. This allows the bag to be fully unzipped, opened out and used as a conventional quilt. The 2 zips overlap to prevent heat loss. Having the 2 way zips gives you plenty of venting options if conditions are too warm. There is a large zip baffle to prevent heat loss through the zip.

The slighly tapered rectangular shape gives you plenty of wriggle room. There is a draw cord at the header for a snugger fit if required with a neck collar to further keep in the warmth. There is a handy zipped pocket at the header for keeping useful items close by, secure and also warm which is great for preserving battery life.

- Reviewed by Ultralight Outdoor Gear

Help and advice: Choosing a sleeping bag advice
  EN 13537 rating for sleeping bags explained
  Sleeping bag shape and sizes advice
  Sleeping Bag features Page 1
  Sleepin bag features page 2
  All about down filling in sleeping bags
  • Tapered rectangular shape for more space and comfort than a traditional mummy bag
  • RDS 650+Loft Ultr-Dry Down offers excellent insulation and compressibility
  • Lightweight fabrics for reduced weight and bulk
  • Vertical chest baffles prevent down migration and cold spots
  • Two way #5 YKK side and separate foot zip allows the bag to double as a quilt and provides extra ventilation
  • Oversized zip draft tube with anti-snag material
  • Large internal security pocket
  • 3D side-wall baffle maximises down insulation right to the edge of the bag
  • 3D hood draws in tight when needed
  • Trek Tk3 has additional neck collar draft tube to seal and trap in all your warmth
  • Soft touch 20D lining fabric is lightweight and highly breathable, durable 30D Nylon shell
  • Includes lightweight Ultra-Sil compression bag for compact storage
  • Zip Coupling: This bag is designed to pair with another

Temperature Rating

  • EN13537:2012 Comfort: -5°C / 23°F
  • EN13537:2012 Comfort Limit: -11°C / 12°F
  • EN13537:2012 Extreme: -30°C / -22°F

Regular Specs

  • Weight: 1176g (excludes storage bags)
  • Fill weight: 700g
  • Fits up to: 6 ft / 183 cm
  • Internal Width Shoulder: 152cm / 60 in
  • Internal Width Waist: 146cm / 57 in
  • Internal Width Feet: 102cm / 40 in


  • Insulation: RDS 650+ Loft ULTRA-DRY Down
  • Shell: Ultralight 10D Nylon Shell
  • Zip options: Full length left side and foot box zipper. Unzip fully to use as quilt or comforter.
  • Comes with: Ultra-Sil Compression Sack & Storage Cube
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