Natural Motion Technology For A Quick Milk Flow,One Size Soft And Adaptive Silicone Cushion,Express Without Leaning Forward,One Size Fits All. Because We All Come In Different Shapes And Sizes, The Silicone Cushion Gently Flexes And Adapts To Fit Your Nipple. It Fits 99.98Percentage Of Nipple Sizes (Up To 30Mm).