This is Red Squirrel Bushcraft Co's flagship product and for good reason.

With a full loadout of around 51L the RSBC "Adventuralist" is a multipurpose, convertible, expandable, and durable bugout backpack.

• Military grade 1000D abrasion and tear resistant fabric with a PVC back coat
• #10 YKK Zippers fitted with cord pulls for easy, reliable access and smooth opening and closing
• Straps and buckles that provide the versatility in loadout configurations needed for a variety of environments and expeditions.
• 3L detachable shoulder pack designed to be configured either on the back of the pack to form a compression pocket, on the top to form a lid for the pack, or to mount in the chest position (using additional clips or lanyards) for easy access while on the move.
• Lots of molle, variable strap lengths and buckle layouts provide additional anchoring points for molle pouches (sold separately) or for bundling a sleep role or sleeping system, and other attachments as desired by the explorer.
• Back support PE board between pack padding and bladder pouch for back stiffness, while the lower waist and upper chest straps helps distribute a comfortable pack load.
• 28-30L main compartment contains a mesh zippered pouch for valuable and other novelty items. 
• Two large 2.5L #10 YKK zippered pouches providing significant storage room for additional gear.
• Hip Belt that can be removed for lighter trips;
• Bottom 5" expandable compartment, separated from the main compartment contains a grommet drain hole to allow water to escape. 
• and more...

See Quebec Preppers product review: 

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