Source’s mid-sized pack is a relatively simple and effective enough cargo bag but you need to be diligent with hose hygiene.
The broad ziplock top 3l Widepac bladder allows for easy filling and cleaning, and the hose is detachable. The braided hose outer means you can’t see gunk building up in it though, and the right-angled bite valve is very hard to remove and replace. This makes ‘pull through’ cleaning very difficult and conscientious use of cleaning tablets is essential, especially if you’re running with fast fermenting energy drinks.
The bite valve flow is slow too, although the dock on the strap to keep it clean is a neat touch.
The bag is slightly stiffened to improve ventilation between the four back pads. The simple strap system, with chest whistle works okay unless it’s particularly heavily loaded and you’re hard on the brakes down a steppy descent, but in all fairness that’s true of a lot of packs.
Zipped deep mesh hip pockets are useful for instant access to tools, snacks, a phone and so on, and there’s a range of sub pockets in the usefully expandable main compartment and lower annexe section. The cargo net in between the two would be a lot more useful if it came up higher though.