Great Trainer for Downtime
For it's cost, you can't beat this thing. I use it at work and in the car for a good pump. I either do reps or time- diamond intervals 30 seconds on, 30 seconds off... 40 seconds on, 40 seconds off... up and back down again. The only thing that's hard to do is opposition training where you are flexing your hands and fingers outward. You can put your fingers inside the ring to do that if they are small enough, but I'd highly suggest doing finger extension exercises in a bowl of rice (you can find vids on this) to prevent injury.