I like these clamps, as they give the right amount of pressure without being downright painful. Their length is good and the adjustable metal ring to make it tighter is perfect, as it gives you more control to adjust pressure quickly, rather than with screws.
I have two small complaints, which I didn't want to give, as I like these clamps. One is the rubber tips at the base of the clamps are loose and they fall off pretty easily. I used the clamps with the nipple in the middle, and not with the tips, so it wasn't an issue. However, those using the tip end, which is more common, will probably have to superglue the ends first. Another is, and this is from personal experience, is when you're trying to pry open the clamps a little to get it around your nipple (and mine are gumdrop size), it takes a little doing! This could be due to their newness and they're not as pliable.
All in all, these are really great clamps, hard enough for those seeking a decent amount of pain, easy to use and to store. :)