There aren't too many backpacks on the market that offer as much back protection as this. And by protection we mean protection in the armour-plated sense, ideal for freeride biased riders but thoroughly sensible for others too.
Deuter's Attack is essentially a well-designed backpack made to hold hydration bladders and other ride essentials combined with an arched and reinforced back system to offer support and protection to your spine in the event of an off.
There's a main body-section, plus a big side-zip pocket and a small top-zip pocket. Capacity is five litres and it comes equipped with strap-compressible attachment flaps, for carrying shin/ arm protection, and a detachable full-face helmet carrier. Well-vented pads mean that it sits very comfortably on your back and the padded waist straps offer extra comfort and protection. Downsides? Well, it weighs a little more than some of the more minimalist offerings, but that's a small price to pay for this sort of protection.