Active Latch nipples are designed to teach and reward deep, wide, natural latching. By requiring suction AND massaging of the nipple, they are designed to discourage lazy latching, and to ease the transition between bottle and breast;Patent-pending 1-piece nipple means there is only 1 food-contact part to clean No leaks, threads, lock rings, or complicated venting parts;Active Latch nipples pop directly into Twist Pouches (sold separately), eliminating the need to transfer milk from bags to bottles and back again;Feed directly from Kiinde Twist Pouches (sold separately), eliminating the need to transfer milk to bottles Each nipple includes a storage case for protection during transport. The tops of the cases also double as bottle covers;Feeding from Twist Pouches can completely eliminate gas from your baby's meal. The pouch collapses as your baby drinks - eliminating air, and eliminating the need for complicated venting parts