There's More Power Than You'd Think
Willow is so compact and quiet that you might be surprised how powerful it can be. It's certainly not a hospital-grade pump, but it does offer seven levels of suction. For transparency, I haven't had supply issues, so I can't speak to how Willow might affect you if you do. But I can say that I only ever went to level three and was able to pump as much milk as I used to with my old pump.
It's also worth noting that Willow's milk bags have a four-ounce capacity, but because of the air that initially gets into the pump during suction, the app will often tell you that your milk bags are full before you hit four ounces. When I spoke to the Willow specialist about this issue, she told me that as I got more comfortable with the pump, I'd see less air in the bags and thus have a higher milk capacity. The most milk I collected in one bag was 3.4 ounces after a week of use. But if your milk bag gets full, you can break suction, insert a new bag, and go back to pumping pretty easily — a small inconvenience that didn't bother me when you consider the overall inconvenience of using a traditional pump.