bought medium strength, little soft in my opinion. Biggest problem is that it is too small; it's no bigger than an actual large chicken egg.
This results in a limited range of motion as you squeeze, so it doesn't work the complete muscle. No exercise suggestions are included either as with other hand exercisers but it's not complicated to figure out.
All in all, it doesn't really fit the bill as a hand grip exerciser, more of a stress relief toy.