Thai Pain Sticks are very easy to operate nipple clamps which leave the nipple still accessible for play
Mister B sells this set of two, each consisting out of 23 cm long metal rods which are held together at each end Put the nipple (or other genital parts) in between the rods, and gradually increase the pressure on them by sliding the two rubber rings towards the middle
Once applied, rotating these Pain Sticks is big fun
Because the nipples are still accessible for play with Thai Pain Sticks on, other stimulation methods remain options Consider licking them, temperature play or putting on another pair of clamps