A correctly sized breast shield is essential for effective pumping. Every woman is unique - one breast shield size does not fit all. For this reason, Medela offers five PersonalFit breast shields with different tunnel sizes to match your personal needs. Help to optimize your milk flow by choosing a correctly-fitting breast shield.For effective pumping, combine PersonalFit breast shields with Medela breast pumps: Freestyle, Swing maxi, Swing, and Harmony.Features:Combine PersonalFit breast shields with Medela breast pumps for efficient pumping.The PersonalFit breast shields are designed for an individual and personalized fit.The interchangeable breast shields are available in five different sizes and are made from BPA-free materials.