This bundle from Dr. Brown's includes a narrow 8 oz/250 mL sippy straw bottle and a wide-neck 9 oz/270 mL sippy straw bottle, both designed to help babies 6 months and up transition from bottle feeding to cup drinking. The soft 100% silicone weighted straw in both bottles moves with the liquid so baby can tilt and sip from any angle, developing upright drinking skills. Sturdy removable silicone handles promote motor skill development and easy gripping. Spill-proof lids keep straws clean. The narrow bottle fits all Dr. Brown's 8 oz narrow-neck bottles, while the wide-neck bottle fits all 9 oz Dr. Brown's wide-neck bottles. The lids and handles are interchangeable between narrow and wide bottles in the Dr. Brown's line. With this bundle, you get two transitional sippy straw bottles that allow baby to continue using familiar Dr. Brown's bottles while learning to tip and sip. The weighted straws and easy-grip handles help develop motor skills, while the versatile, interchangeable parts provide a coordinated set for bottle feeding through the cup transition stage.