If you roll them up, id say about a nalgene and a half... I just stuff em in my 7900 ci bag and go.This look pretty great! Do you know what the final weight is on these? Also, how small are they when packed down? I'm doing a 7 day drop-camp caribou hunt in late Sept, so it's going to be cold, but I also need to worry about weight and space, as we are limited. Hoping these might be a low-cost, but effective, choice.