I bought the nipple cylinders as a surprise for my submissive female lover.
I regularly began pumping her nipples up with increased suction, as time went on she would often moan with pain but our agreement was that she would succumb to all of my dominant desires. I would leave the small cylinders on her nipples for about 10-20 minutes during foreplay and then release them. Her turn-on is that I do whatever I want to do to her.
One day I decided it was time to go further.
After a good pumping session I removed the cylinders after an extended 30 minutes and her nipples were bright red and unusually swollen. I drove two pins through her swollen nipples, from the bottom to the top. She screamed in pain but being gagged and bound her screams went unattended to.
Later she confided to me that she had experienced the best orgasm/excitement of her entire lifetime.