First Essentials Silicone Nipple work with the #1 selling, reusable baby bottle in the U.S.A. as well as most standard reusable bottles. They help reduce colic with a vented nipple design. Plus, vent holes and ribs help ensure smooth flow and limit nipple collapse. </br>Features: </br>Fits most standard reusable bottles. Helps reduce colic with vented nipple design. Vent holes and ribs prevent nipple from collapsing. Dishwasher safe. Silicone, Medium Flow (6-18m).