Comes in: 21, 24, 27 or 30mm The new PersonalFit Flex™ breast shield was developed with the help of a team of research scientists and breastfeeding moms. It’s designed to easily adapt to your shape, and encourages your milk flow by helping prevent compression of the milk ducts. This makes it easier for every mum to find the pumping position that’s most comfortable for her. The result? More comfortable, more efficient expression, shaped around you.