Medela's PersonalFit Connectors are engineered, tested, and approved to work specifically with your Medela Pump In Style Advanced and Symphony breast pumps and seamlessly attach to all PersonalFit breast shield sizes. Understanding your breast shield size and ensuring a proper fit is essential for both comfort and optimal milk expression. The PersonalFit connectors easily attach to all Medela PersonalFit Breast Shields including the PersonalFit, PersonalFit Flex, and PersonalFit Plus. Keep an extra set of connectors around so you always have clean parts on hand. Refer to the breast pump instructions for complete cleaning and assembly instructions.