Been using these for several years - unfortunately have had to buy several pairs over the years as I have ultimately broken them applying maximum tension. Have 'tweaked' my nipples so hard and so often that after a gentle start I can use three of these on each nipple, gradually tightening each one progressively. God that is good, just 'ride out' the pleasure pain. Keep on for a while - 10-20 minutes and when released - wow another sensation! Start gently and work up, it'll be worth it!