The worst thing about most hydration packs is the bladder. Most bladders are hard to clean and accumulate gunk without you even realising it. It can get pretty nasty. If you've had enough of disgusting hydration bladders or want to avoid it altogether, consider Jetflow's hydration system. The JetFlow uses normal water bottles of drinks you can buy at the grocery store instead of bladders and there are adapters for different size bottles. Great if you tend to avoid washing hydration bladders even when they're relatively easy to clean. It can hold up to a 2-litre bottle depending on the size of the pack.