Using dry bags inside the pack means you: * Don't need to stop/remember to put the pack cover on. * Can use them to organise different things. e.g. separa

Using dry bags inside the pack means you: * Don't need to stop/remember to put the pack cover on. * Can use them to organise different things. e.g. separate clothes from sleep kit. * Can use them to roll/squash the air out of clothes/bedding to take up less space. * If you need to remove things from the pack to look for items lower down they'll stay dry in their separate bags. The trade off is a little more weight but it's generally < 100g-ish compared to a pack cover.