How do I know if my medela breast shield is the correct size!!!!!!

Brandy • Sun, Feb 11

So I have the generic size 24 mm that came with the pump. And when at the hospital I was using another kind of pump and now at home and I think maybe my freestyle is not working right or the shield is wrong or something. It just can’t pump out the milk like the one at the hospital. How do I know if it’s the shield size?