These are some wicked clamps! Rumor has it they were invented by a Japanese seamstress, but I have no idea if that is true or false, so please, don’t quote me on it. What I DO know is that these babies start with a tight, firm pinch and with each minute tug on the chain (or anything else attached to them) the tighter and firmer the pinch becomes. USE WITH CAUTION.  Nipples are very sensitive and the tissue can be easily damaged. With that in mind, I suggest that you begin very, very slowly. Attach not for minutes, but for seconds and then work your way up as your tolerance grows.