I ordered the captains from the states, you can buy them here but even when I factored in postage they were cheaper, something like $35 each... I got 1, 2, 2.5 & 3.
The strength they build doesn't translate to deadlifting (well not much) or static holds. Closing them the way most do only really works the pinky/ring fingers, too.
They are good for boasting and competing with your mates but I don't think they are great for much else, and this goes for all spring based tools. As you compress a spring it gets harder to close, so the max resistance is at the very end when the handles are almost touching, before that there's not too much.
I can close up to the 2.5 but not the 3.......... been trying for a while but it is a car spring. I found 70% of guys can't close the 1 and probably 99% of guys can't close to 2 without training for it. I guess they are better than nothing but I'll probably stop training with them once I get the 3, they are hard on my joints.