Just wondering if anyone has used these/ seen them and what your opinions are, to me it looks like a new ...fad but maybe a useful tool. ( I say fad in the sense of the mass market i.e kettlebells, olympic lifts ect but obviously still useful tools !) Im working in a fitness club so get a free taster session so will let you know my opinion when i do. Just wondering if anyone has any experience From what i can see they look like the classes are aimed at conditioning and muscular endurance more than anything.