The Sierra Designs Flex Capacitor 40-60 M-L is an ultra-lightweight backpack with a unique patented volume expansion system for travelling, hiking and trekking.
A wedge-shaped insert in the front and a system of webbing straps help to adjust the volume of the backpack by increasing or decreasing its width - this provides a more stable and comfortable load, unlike backpacks with an increased vertical part.
The suspension has a removable, collapsible aluminium Y Flex DAC frame in the shape of the letter Y. This system conveniently distributes the load with an emphasis on the hip belt and creates space for ventilation and dispersion of warm, moist air generated during long walks between the backpack and the back.
The straps, hip belt and back cushions are made of moulded foam with perforations and air channels and are lined with mesh material.
The hip belt with two voluminous pockets is equipped with a convenient "reverse" tightening system - to tighten the sling, you need to pull forward instead of backwards.
When transported as hand luggage, the belt and frame can be removed.
Thanks to its design features, the backpack can be used for a wide range of outdoor activities, hiking, travel and travel, where it can also serve as hand luggage during flights.
The Sierra Designs Flex Capacitor M-L is a model with a back size of M-L (for medium to tall users) and is available with a hip belt in one of two sizes, S-M or M-L.
The backpack was designed by the famous athlete and traveller Andrew Skurka and received prestigious American awards:
- One of The Best Summer Packs of 2017 by Outside Magazine
- Top Gear of the Year 2016 by GearJunkie.
To protect your backpack from dirt and heavy rain, we recommend that you additionally purchase the Sierra Designs Flex Capacitor Rain Cover grey or its equivalent.

Features of the Sierra Designs Flex Capacitor 40-60 M-L backpack:
- Volume, litres:   42-60 (2563-3661 in3)
- Backpack weight:
   - 1.16 kg (2 lbs 9 oz) - with S-M harness system
   - 1.19 kg (2 lbs 10 oz) - with M-L hip belt system
- Height, cm:   70.0  (27.5 in)
- Width, cm:     28.0  (11.0 in)
- Depth, cm:     25.4  (10.0 in)
- Materials:   100D Nylon-Poly Ripstop, 420D Nylon Oxford, DAC Pressfit Aluminum
- Suspension:   Y Flex - backpack frame made of extra-strong Y-pillar made of DAC Pressfit Aluminum
- Curved back allows air to circulate freely and provides ventilation
- Soft ventilated EVA foam cushions on the back in the lumbar and shoulder blades
- Padded ventilated shoulder straps and hip belt made of EVA foam
- Shoulder straps equipped with chest and stabilising straps
- Adjustable hip belt with zip pockets
- Belt system in two sizes:   S-M - 66.0 - 97.0 cm (26- 28 in) and M-L - 84.0 - 122.0 cm (33- 48 in)
- Tie-down straps on the front of the backpack for changing the volume and hanging equipment
- Vertical loading with U-shaped top zip
- Side elasticated pockets with thick fabric inserts for a flask, poles or frame poles
- Elasticated flask pocket on the right shoulder strap with tie-down and clip
- Flat pocket in the lid of the backpack
- Two voluminous pockets on the belt
- Removable pocket for drinking system inside the main compartment
- Two elasticated pockets for phone or flask on the shoulder straps
- Textile loops for ice axes or trekking poles
- Colours:   bering blue, peat

Warranty
The warranty period is 1 year.
If a Slumberjack product fails due to a manufacturing defect, we will repair or replace it free of charge at our sole discretion.
This warranty applies only to original, unaltered and unmodified products and workmanship.
This warranty does not cover damage caused by accident, improper care, negligence, normal wear and tear, weather conditions (wind, rain, fire, animals, etc.) or natural fading of colours and materials.
This warranty does not cover consequential damages or any other damages resulting from any defect in the product.
Damage not covered by the warranty may be repaired at a reasonable cost.
Manufacturer:
Slumberjack or SJK was founded in 1959 in St. Louis, Missouri, USA.
For many years, the company has been producing sleeping bags for children, adults, double sleeping bags, tents and camping furniture, as well as a lot of related equipment.
Until the last moment, everything was produced in the United States, which greatly distinguished the company from all competitors and eventually turned it into a strong player in the outdoor equipment market.
In 2008, Slumberjack became part of American Recreation Products, Inc. (American Rec), which by that time already included Kelty, Sierra Designs, Ultimate Direction and others.
In 2014, the company presented a new direction - Tactical Hunting Gear, in which it formed and implemented multi-platform solutions for hunting, which included transformation, various combinations and were quite versatile. The company's innovative developments were implemented in various colour combinations - DST (Disruptive Shadow Technology), Kryptek and Realtree MAX-1 camouflage. Tactical Hunting Gear also includes pouches, mats and covers for weapons, as well as warm waterproof raincoats.
In April 2015, American Recreation Products (Slumberjack was part of this corporation) merged with Exxel Outdoors to become a leading provider of high-quality and innovative outdoor products and the largest sleeping bag company in the United States. The newly formed corporation united the well-known brands Slumberjack, Kelty, Sierra Designs, Ultimate Direction, Wenzel, Insta-Bed, Tadpool, Master-Sportsman, X2O-sports, and Serta.
Today, Slumberjack is the perfect modern solution for hiking and camping, with a wide range of backpacks, sleeping bags, tents, mats, camping furniture and accessories.
Slumberjack provides a wide variety of options for maintaining comfort during outdoor and open-air activities.
Slumberjack hunting backpacks and equipment are lightweight and durable, which guarantees reliability and allows you to fully concentrate on the hunt.