No more bulky backs this 25l pack combines the superior vpd back protector with a hydration pack and extra compartments for tubes energy bars rain jacket wallet and keysthe packs come in two different sizes depending on how much you need to carry and they are equipped with smart pockets to get everything at the right place water tube gare with neoprene lips padded mobile and key zipped pocket ergonomic shouler strap heat molded back to optimise moisture transportation