Instead of buying several trail packs in quick succession after realizing yours are continuously too big, too small, or without a feature you didn't realize you needed, you could invest in a pack like Shimano's Unzen Bike Hydration Pack with Resevoir. With a versatile size that won't weigh you down on short days but will still hold everything you need on longer adventures, the Unzen comes with a Hydrapak hydration system, as well as the ability to hold and organize everything you'll need on a ride. Whether you're traveling further afield or pedaling along your local singletrack, the bag comes with a tool organizer pocket, a fleece lined pouch to protect the surfaces of electronics and sunglasses, and space to store lightweight body armor or a jacket on its exterior. It's also dotted with an array of other more general use pockets, as well as an outer helmet holder to make packing up for a drive to the trailhead easier, and a removable waist belt to keep the ache out of your shoulders on longer days. While your stuff stays organized, you'll stay cool and dry with the bag's breathable straps and back panel, designed to keep you comfortable during hot days and exposed rides.