Options Bottle can be used with or without Vent system;Helps reduce feeding problems - colic, spit-up, burping and gas;Proven to help preserve bottle milk nutrients;Vacuum-free feeding helps digestion;Each bottle comes with 1 Level-One silicone nipple, 1 two-piece patented internal vent system; 1 cleaning brush and instructions;The market's first convertible bottle that can be used with or without the vent system;The new vent system is designed to grow with baby, and we recommend using this system to experience all the health benefits of our bottle;With the vent, benefits include: helps reduce feeding problems our bottles are known for reducing colic, spit up, burping and gas proven to help preserve bottle milk nutrients;Want the convenience of a nipple-vented bottle without the vent, options provides a feeding experience similar to most nipple-vented bottles;This nipple venting creates a controlled flow, offering babies an easy and convenient way to feed at their own pace