Used mainly as my stalking backpack, I have now replaced it with a larger eberlstock pack.
It is a standard Camelbak esque bag, but with the addition of two useful pockets. I used the top one for holding binos, and the lower one for snacks, knife etc.. It also has molle loops on the front and I had a couple of single pouches with a torch and bits in them. All in all, very versatile.
Very similar to the latest model linked: Here, except mine doesn't have the velcro above the molle loops on the front of the bottom pocket.
Photo of mine:
Bought it to take to Africa, and it was cracking. When I started using it for stalking in this country, I sprayed it with some green krylon type paint through a mesh filter, to dull the lightness of the desert camoflauge. This is probably not reversable, but I think it makes it a lot more in keeping with the colours of UK woodlands!
It does not include the hydration pouch, but if I was buying something like this second hand I think I would want to buy a new one anyway. A brand new 2 litre hydration pouch can be bought new on eBay for under £10.
I would like £30 posted and paypalled for this great little bag