Sierra Designs Flex Capacitor 40L-60L Blackpack With Waist Belt - Peat

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Size: S/M

The lightweight backpack of your dreams is here. Meet the versatile pack that hauls it all. The Flex Capacitors is a beast of backpacking pack, constructed from durable nylon for rough conditions in the backwoods and built with adjustability in mind. Loosen the expanding horizontal gussets for an additional 15-20L of cargo capacity on longer backpacking trips, or cinch it tight for smaller, compact loads on fast summit days. Plus, ample quick-stash solutions on the straps, sides and bucket lid ensure there are plenty of places to store your mid-trail essentials. However, you pack it, the Y-Flex suspension adds support so this lightweight backpacking backpack can hit well above its weight class.


  • Expandable volume for versatility in use
  • Dual adjusting shoulder straps tailor to torso fit
  • 2 hyrdation pockets on shoulder straps
  • 2 stretch mesh side pockets
  • Hydration sleeve doubles as removable summit sack
  • Zippered hipbelt pockets
  • U-shaped top access zipper
  • Lightweight Y-Flex Suspension
  • Ultralight weight



  • Weight: 1258g
  • Volume: 40-60 L (2441 - 3661 cubic in)
  • Waist Belt: 28” - 46” (71 - 117cm)
  • Torso: 16” - 19” (41 - 48cm)


  • Weight: n/a
  • Volume: 40-60 L (2441 - 3661 cubic in)
  • Waist Belt: 33” - 50” (84 - 132cm)
  • Torso: 18” - 21” (46 - 53cm)

Material & Construction

  • 420D Small Back Stafford Poly


Delivery Details

In-stock items are dispatched the same day if ordered before 2pm (Monday - Friday) or the next working day if ordered after 2pm or on a weekend.

Deliveries are normally next working day for orders over £60. If under £60, we sometimes use a 48 hour service. You will have the option to upgrade to a next day service at the checkout.

Special Order items are dispatched within the timescales displayed after selecting your size.

Most orders are dispatched using DPD Next Working Day.

We use Royal Mail 24 for the more remote parts of Scotland, the Channel Islands and Northern Ireland. Please allow a little extra time for delivery in these areas.

For orders under £60, we normally dispatch using Royal Mail 48 with delivery being made in 2 to 3 days. You will have the option to upgrade to a next day service in the checkout.

A tracking number will be emailed to you for all orders over £60 on the day of dispatch.

For orders under £60 dispatched using an untracked economy service, a reference number will be emailed, but you will not get full tracking, only confirmation once delivery has been attempted.

Other Questions

Sometimes you will see 'Special Order' when selecting your size. For these items, we will dispatch once we have received them from our supplier.

An estimated lead time will be displayed for Special Order items.

Yes, returns are accepted within 30 days of purchase so long as it is unused and still in it's original packaging*.

You can return for an exchange or refund.

Refunds are carried out immediately after receiving your item back. Return postage is at your own cost.

* for safety reasons, we do not accept the return of climbing equipment or underwear once it has been tried on.

All items sold come with a minimum 12 month warranty that covers defects in materials or workmanship.

Certain brands offer an additional warranty. You can find this information on the brands own website, or you can contact us for additional information.

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