In reply to Steve Ward:
Right, I have just purchased a Mountain Equipment Diamond 50+ climbing/alpine sac (in black ooh!though you also get red and electric blue) - by far the BEST wee sac I have ever ever ever bought and i've had a few(11 of various sizes and makes)
Comes in 3 sizes small, med and large - I'm 5ft 8 so med is perfect. Infinitely comfortable (fully loaded with essentail winter gear)- adjustable bits for fit, removeable strut in the back - all the usual perks..side compression straps (2 each side)..adjustable bungee cord crampon holder thingy on front.....twin daisy chain jobbies on the front....
plus it has lid exterior and interior pockets, seperate locking system underneath main closing clip thing, bomb proof bottom, two really strong gear loops (much akin to the ones you get on your harness)on the waist belt....oh the list goes on.
I had it ut in torrential rain yesterday and although we know no sac will keep your stuff totally dry unless you use waterproof liners, blackplastic bags etc..this was really quite good.
I'd thoroughly reccommend it! Cheap too......down from £90 to £40 at Rock and Run, though mine was on back order and i don't know the supply situation.