The ERGO Baby Carrier back pack attaches right onto your Ergo carrier! The backpack snaps around the straps of the baby carrier with four relatch buttons. The backpack is made of 12 oz 100% cotton canvas, and is 14" x 14" x 4" deep. The pack has two front pockets, an attached bottle holder, and a side zipper pocket for easy access when being worn. Shoulder straps mean this pack can also be worn independently of the carrier! Top handle for easy toting.