Green to Grow's silicone nipples are made from a transparent, medical grade silicone that is heat-resistant, non-toxic, and odorless. The nipples are free of nitrosamines, a potentially harmful contaminant found in many rubber nipples. They come 3 nipples per package, 3 speeds to choose from: beginner (slow flow, 0-3 months), intermediate (medium flow, 3-6 months), expert (fast flow, 6+ months); dishwasher safe.