[BongoGirl1]

I use the Kangzhu large cups and I don't have permanent ring marks. I pump at kind of high pressure, but never to the point that it hurts. When it hurts I release a little bit of the pressure until there's a comfortable pull. Every 20-30 mins I release the pressure completely, pull the cups off and take a couple minutes worth of a break. Then I put them back on. I do this for two hours every evening six days a week and it works well for me. Your white ring marks are probably from cutting off circulation. I recommend using low pressure if you're going to sleep with them on because it can destroy the tissue under the rings if circulation is cut off for too long. Hope that helps!