Whoever came up with the aircore design deserves major props because my back stays pretty darn dry! One of the downsides to this pack though is that you can't pack as much because of the darn thing! it's a cool pack but I'll be honest, I prefer my BD RPM for a smaller volume pack because it weighs HALF as much and holds a little bit more than the stratos AND it's cheaper by alot of dough if youre a price conscience guy like me. HOWEVER... I picked this one up on a sale which is why I bought it and it's a great piece in the collection. Good pack and very unique design!