love them..
though if you get big into them the heavy grips are child's toys...
i like tetting grippers. Grippers like the grand master, elite, and super elite...all of them I use. All are VERY well made and have a smooth transition through the sweep. I like COC stuff since it seems to be the staple but all grippers have some varying degree of difficulty even if they're both the same make and model. I can close a coc 3.5 with both hands but there are some MONSTEROUS 3.5's that I can't shut period. Too..don't get caught up in what the "rating" is like 365lbs or whatver because that's a load of shit. The actual crushing weight needed to close a 3 for example is around 140lbs and the weight or power in ones' hand needs to be around 166lbs of crushing power to close a 3.5.
I compete in grip strength contests...love me some grippers. check out grippersuperstore.com for all kinds of grippers. It's THE place wiht all brands, ratings, etc.