So...the most difficult trainer was the one I bought first; I figure it's relatively light weight, shouldn't be a problem. After trying it out for a day.i ended up buying the lower two trainers the next evening.
I was Impressed at what it did, how challenging it was, how it felt, and could tell it would absolutely help my routines. I could also tell there was no way in hell I'd be able to get it going and use it normally without working my way up.
It is QUITE challenging, getting the three balls to rotate smoothly in the tube, and while your trying to get the rhythm, your shoulder will be absolutely dying. When I got the other two, it takes a bit to get used to the flow, even with the single ball.
I love these trainers, they will be a lifelong addition to my warm-ups, conditioning and general training. Hits the shoulders like nothing really out there, and when you've been using it a while, it makes you wonder why no one has come out with something similar sooner.
An absolute beast to add on the journey to bulletproof one's shoulders, and any athlete, professional or hobbyist, should seriously consider them. This is the type of fitness innovation we need more of.