Hydro Flask Standard Tag Along Bottle Sling. Take your Hydro Flask with you, but keep both hands free to paddle, climb, or high-five at the top of the hike. The sling was designed to make hydration on the go easier than ever. Standard size fits 12, 18, 21, and 24 oz standard mouth bottles. Welded webbing and attachment mounts for extra durability. Fully adjustable, stretch-woven, Sliplok shoulder strap. Stretch-woven and bonded side pocket with waterproof zipper for storing essentials. Imported.