This is a tough nipple that can withstand aggressive nursers yet is soft and pliable. Made with a special rubber formula for long life and improved pliability. This nipple style must be used with a Little Giant Screw-On Nipple Cap (Item Nos. 93SC and 93SCPK, each sold separately); the nipple does not attach to the bottle with out separately purchased Screw-On Cap. Nipple is 1 inch diameter by 3 inch long.