I don't even know how to sum this up to search for it. When I'm pumping, I noticed that if I apply pressure to the flanges at different sides once milk flow has slowed down, I get a faster flow again like when my milk lets down. Does this mean I should use a smaller shield? I'm currently using a 27mm as directed by the LC in the hospital. I had to pump while my daughter got formula to help flush out her jaundice during phototherapy. I have a set of 24mm and I'm wondering if I'll see better results pumping with these? Any ideas!