Made from a soft yet rugged silicone, the GoToob+ has a large opening making it easier to fill and clean. The bases are contoured so that they can stand up easily for filling.A lockable collar makes it almost impossible to accidentally open the cap, reducing the chance of leakage, and provides a handy loop to hang the tube from a hook or clip it to the outside of a pack. There's also a textured area on the collar to write in the contents with a permanent marker.