Additional collars and transparent covers are sold separately allowing mothers to seamlessly convert a storage container to a feeding bottle. Simply pair it with a teat flow of your choice (extra slow/slow/medium/fast/thick feed) to experience the multi-functional, modular benefits of Hegen’s Express-Store-Feed system and enjoy the convenience of a hassle-free conversion when it comes to feeding.   Directions for Assembly: – To remove transparent cover With the Hegen logo on the Collar facing you, push the Transparent Cover backwards (away from you) to open.   – To assemble teat into collar Step 1: Gently squeeze the anti-colic air vent to ensure it is open. Step 2: Place the Collar over the Teat Step 3: Pull the Teat through the Collar until it is snugly fitted. Tip: Press on all 4 sides to ensure Teat is fully secured. Place on the Transparent Cover for hygiene purposes.