Playtex Drop-Ins Pre-Sterilized Disposable Liners are pre-formed, so all you have to do is simply place one in a Playtex Nurser and fill it. Sanitary and convenient, these disposable drop-in liners ensure a clean bottle every time and easy cleanup after feeding. Twist on the nipple and ring and you"re ready to feed your baby. You will receive 50 count of 4 ounce liners.