Sea to Summit Trailhead ThIII 20 Sleeping Bag

$179.00to $199.00
Color: Midnight Blue
please select a Size
Choose a shipping method

Great for weekend warriors and new campers, the feature-packed and value-oriented synthetic Sea to Summit Trailhead ThIII 20 sleeping bag is no slouch when it comes to performance.

  • Features

    • Tapered rectangular shape offers more space and comfort than a traditional mummy bag
    • Full-length #5 YKK zip allows bag to open out flat and be used as a quilt
    • Second zip slider in footbox offers versatile ventilation
    • WaveLoft™ construction creates extra warmth and loft
    • Lining fabric attached to shell prevents tangles
    • Oversize zip draft tubes feature antisnag material
    • 30-denier nylon shell treated with durable water repellent (DWR) and 20-denier nylon lining are lightweight and compressible fabrics
    • Includes stuff sack
    • Note: This bag is not designed to zip with another


    Many sleeping bags are rated for temperature by an independent testing protocol. REI and the broader industry now use the International Organization for Standardization (ISO) 23537 protocol, which improves on the older European Norm (EN) 13537 standard; you may still see older items in our assortment that were only EN tested. With either protocol, each bag gets a Comfort (or T-Comfort) rating and Lower Limit (or T-Limit) rating. The Comfort rating is the lowest temperature at which the bag will keep the average "cold sleeper" comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average "warm sleeper" comfortable. Ratings are based on a person wearing one long underwear layer and a pair of socks, sleeping on an insulated surface with a minimum R-value of 5.38. Many brands use the Comfort rating for women's bags and the Lower Limit rating for men's and unisex bags. Everyone's body and sleep comfort differ, and conditions of use (posture, clothing, sleeping pad R-value, wind, humidity, etc.) affect total insulation, so EN and ISO ratings are intended as a guideline to help you compare products, rather than a guarantee of warmth.
    View all Sea to Summit Backpacking Sleeping Bags
  • Technical Specs

    Best Use


    Tested Lower Limit

    20 degrees (F) - EN

    Tested Comfort

    31 degrees (F) - EN

    Temperature Rating (F)

    20 degrees (F)

    Temperature Rating (C)

    -7 degrees (C)


    Regular: 3 lbs. 1 oz.

    Regular Wide: 3 lbs. 6.6 oz.

    Long: 3 lbs. 5 oz.


    30-denier nylon

    Zipper Location


    Insulation Type





    20-denier nylon

    Sleeping Bag Shape


    Fits Up To (in.)

    Regular: 72 inches

    Regular Wide: 72 inches

    Long: 76 inches

    Shoulder Girth (in.)

    Regular: 60 inches

    Regular Wide: 68 inches

    Long: 64 inches

    Hip Girth (in.)

    Regular: 57 inches

    Regular Wide: 63 inches

    Long: 62 inches

    Stuff Sack Size


    Stuff Sack Volume


    Compressed Volume




  • Reviews
    7 reviews with an average rating of 4.3 out of 5 stars

    Loading Reviews...
  • Questions & Answers

    Loading Questions...