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Sierra Designs Flex Trail 40L-60L Hiking Backpack

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Explore like a pro no matter your experience level. The Flex Trail ultralight backpack gives you the ability to tailor the pack size to your adventure needs by taking advantage of the horizontal gussets. Cinch it down to a 40L cargo pack capacity for your shorter trips. Expand it out to 60L for your longer backpacking adventures. Continue to customize your backpack with the hardware-based adjustable torso. Keep your essentials close at hand with oversized mesh pockets and zippered hip pockets. The aluminum perimeter frame suspension keeps this backpacking pack lightweight while the support stays strong.

  • Expandable volume to adjust to both short and longer backpacking adventures
  • Lightweight aluminum perimeter frame for increased stability
  • Customizable fit with a hardware based adjustable torso
  • Large front stretch mesh Shove-It pocket to easily store jackets and other day essentials
  • Zippered hip belt pockets and 2 stretch mesh side pockets for storing water bottles and items you need to keep on hand
  • U-shaped access to top zipper and zip stash pocket in lid to store items for easy access
  • Ultralight backpacking backpack
  • Capacity: 39-56L / 2380-3417 in3
  • Weight: 2 lbs 12 oz  / 1.23 kg
  • Optimal Carry Weight: 15-45 lbs / 7-20 kg
  • Torso Fit: 15.5" - 21" / 39 - 53 cm
  • Waist Belt Size: 31" - 54" / 31 - 54 cm
  • Dimensions (H x W x D): 27.5" x 10.5" x 14" / 70 x 27 x 35 cm
  • No. of Hip Belt Pockets: 2
  • No. of Exterior Pockets: 5
Delivery Options

  Standard Delivery

Free Delivery on orders over £30 and £2.95 for orders under £30.

  • Delivery is within 2-4 working days, ordered before 1pm
  • Your order will be delivered by Royal Mail or UK preferred Courier
  • You will be notified when your order is despatched

  Express Delivery

Free Delivery on Orders over £500, £5.95 for orders under £500

  • Delivery is within 1-2 working days, if ordered before 1pm
  • All orders over £500 are eligible for free Express Delivery service
  • A delivery charge of £5.95 applies to purchases under £500
  • Please be aware we only deliver to UK Mainland and Northern Ireland
  • You will be notified when your order is despatched


**Please note we only deliver to the UK and Northern Ireland. We cannot take responsibility for any delivery delays or problems out-with our control caused by the weather or any Delivery company. We will do everything we can to help resolve any delivery issues. You will be responsible for the items as soon as they are delivered. If you wish to cancel an order before it has been dispatched, you should call us on 0131 3807205, or email us at:


    Returns Policy

    Thank you for making a purchase with us at PureMtn.

    If you've changed your mind for any reason about the product you ordered, please contact us with your order number at and we will then provide you with a Returns Number and start your returns process of how and where to send the item/items back to us.

    Provided your item is unused and in original condition within 31 days of order (including all labels, tags, product boxes, accessories and bags intact), you can send the item/items back for a refund or exchange. Please ensure all Returns are carefully packaged as they may be refused if items arrive damaged due to improper packaging.

    If a Refund is requested, we will refund the value of the returned goods (not including the postage) to your original payment method within 7 days after they have been received and checked by our returns team.

    Should, for some reason, you receive a damaged or an incorrect item, then please accept our apologies and contact our Customer Service Team immediately on Tel: 0131 380 7205 to allow us to resolve the problem as quickly as possible.

    Please don’t hesitate to contact our Customer Services team on 0131 380 720 if you have any questions about our returns policy. They are here to help you Monday - Saturday 9.30am - 5pm or email us on:


    Should you choose to return your order and request an exchange, the exchange  will be sent the day after your return has been checked and logged, provided the requested exchange item is in-stock. You will be charged for any additional postage. To ensure you get the item you wish, it will be quicker and simpler to order the new item and send the old one back as a return and request a refund.

    You will receive a refund for any difference in price, if a lower value item has been chosen in exchange (minus the cost of any original shipping charge.

    Sierra Designs Flex Trail 40L-60L Hiking Backpack

    Sierra Designs Flex Trail 40L-60L Hiking Backpack

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