Medela Personal Fit Flex Milk Mouth XL, 1.2 inches (30 mm), Set of 2, Use the Right Size of Milk Mouth for Efficient Milking and Gentle Support for Breastfeeding

If the pump is too large or too small, it may not be able to breast well.
Does your nipples rub on the pumping bottle? Do you have too much gap between the nipple tube and the nipple? Are your nipples (including the nipples) too much inhaled during your nipples?
[Recommended for choosing the size of the pump, the diameter of the nipple plus 0.2 inch (4 mm). ]
Nipple diameter ~ 0.7 inches (17 mm); Small size for breastfeeding opening 0.8 inches (21 mm)
Nipple Diameter: 0.7 – 0.8 inches (18 – 20 mm); Size M for pumping hole: 0.9 inches (24 mm).
Nipple diameter: 0.8 – 0.9 inches (21 – 23 mm); Large pumping size (1.1 inches (27 mm).
Nipple diameter: 0.9 – 1.0 inches (24 – 26 mm); Extra large pumping spout size: 1.2 inches (30 mm).

Choose the right size pump, make more comfortable and more breast milk
Medela products are BPA free