I should comment that I use a 2L Osprey Hydraform reservoir inside the back of the Flash 18 for a "frame". It's heavy for a water bladder, but I am happy to accept the jump in weight for how comfortable it stays against my back, even when totally empty. Highly recommended.

I use the same thing for day hikes as I do as my primary summer/shoulder season backpack... the ZPacks Zero in cuben fiber, sized X-Small. 1,000 cubic inches / 16.4 liters.

It is perfect for a day hike or even for a three day hike. Much more than 3 days and I run out of room for food :(

I'm using the EMS packable pack. For $24 (on sale), a 9oz, 1500in3 pack. I haven't trimmed it down yet, but would probably get rid of the internal bladder sleeve. Nice top pocket and mesh side pockets. Would love to make this my SUL pack when I get there.

I'm using a Hydraform bladder as well- the added stiffness outweighs concerns of additional weight over other bladders (the nifty magnetic bite valve holder is slick too :))

Black diamond 22l black diamond, if i need to carry a lot of gear, its got a large external sleeve to stow gear in. great flexible belt and shoulder straps that dynamically shorten and lengthen in opposition, because the shoulder straps are connected by a cable that runs freely under a runner at the base of the pack. you can move fast and free not resistance from hte pack, forget youre wearing it
the zipper won't keep the rain out, if heavy rain is a problem black diamond dont do backs with a lid smaller than 30 litres, they don't tend to do waterproof zippers

Edited by wayno on 11/28/2011 00:04:19 MST.

+1 on the Sea to Summit Ultra Sil. True the straps could be better (theyre not padded) but at 2.4 ounces it has to be the lightest 20 litre pack out there. I made a sternum strap with 1/2 inch webbing and a small side release buckle. I thought this was overkill on such as small pack but it keeps the straps from spreading and digging into my underarm. With the sternum strap the pack weighs 2.6 ounces and cost less than $30.

You fit can fit a shoulder season load into a 16 litre pack???
Jeez there must be some uber small gear out there that my wallet will never let me see.

3 season day hikes - I just use an Eddie Bauer waist pack (Target $20). What I have put inside it:

o 4.8 liters of water (2.8L in the pack and two 1L bottles in the side pockets)
o wind jacket
o lunch and snacks
o bug/sun screen
o small first aid kit
o flashlight
o compass

Carries well... and best of all, a waist pack allows for much easier putting on / talking off wind jacket.

capacity: 250 c.i. according to the label
weight: 8oz actual

Edited by ben2world on 02/11/2012 21:49:48 MST.

"Thanks guys. I am trying to go from using a 30L daypack to something under 20L"

Heh heh... The pack I used for my 7-month RTW travel was 28L.