This site has two different brands of clover clamps. "Pipedream" and "Spartacus". I have both. The Spartacus are about twice as strong as the Pipedream. I prefer the Spartacus because they are stronger and I get to the ecstasy a little sooner because of that.
I am a male with small nipples, so I use clamps to grab a nice chunk of aureolae rather than the nipple itself, it spreads the intensity to a nice dull feeling rather than needle-sharp. Though I can do both, I prefer the dull effect. I like to wear them for up to an hour at a time, as it typically takes that long to reach a fever-intensity I so enjoy. After a few months of experience, this can be enough in itself to stimulate full-on internal howling orgasm!
Things to note: When clamping a goodly amount of flesh rather than just the nippy-nipple, the Pipedream opens a little larger in practical use because the centre stabilizer-slider does not come as far forward on the Pipedream as compared to the Spartacus. The difference is only about 1.5 mm, but I need to be careful sometimes to not have the slider nosing into flesh especially when getting a little rough.
Another reviewer noted that they lost a "pad" from their Spartacus. This happened to me too. Good thing I had a 2nd set of the Spartacus: the second set has performed flawlessly with two years of almost daily abuse.
One more thing - with these clamps, if you leave them on for a long time (like 20+ minutes) you want to be attentive to take them off s-l-o-w-l-y. I do not recommend that you just tear 'em off or allow your partner to tear 'em off. The reason being that removing them quickly without giving your skin time to release from them can cost you the top layer of skin. On the other hand, squeezing them open without attempting removal, then letting them close, then squeezing them open without attempting removal again, back and forth a few times is one way of giving your skin the time to release while at the same time driving you crazy. Which is good!