I chose these clamps because I like their very basic appearance. Despite being so plain, they also manage to look pretty sexy: the combination of black and silver is very kinky and looks like something you'd see in a dungeon.
The clamps are easy to hold onto and don't take a ton of pressure to open. They can get a little slippery if your fingers are lube-y, but other than that, they're easy to use.
As I said before, these give a lot more pressure than I was prepared for (and the pressure is unfortunately not adjustable). I have fairly sensitive nipples, so when I put these on, I always have to stop before I even let go of the squeeze-open part of the clamp, because the pressure and pain are so great. However, for someone with less sensitive nipples or with more experience taking pain, these would probably be ideal.
My breasts are a B cup, and the leather strap is long enough that if I were to put a clamp on each nipple, there would be a couple inches of slack in the strap. This means that you could attach an additional clamp to it if you wanted one to put on your genitals, for example. It also means that it would be easy for a partner to pull on the strap to briefly increase the pain suffered by the wearer.