As someone who goes through phases of obsession with legato and Eric Johnson, I have to say that the blue Grip Master is more than enough if this is your first purchase. What truly matters is your grip technique—if you use it like a fitness tool, the product might seem too simple, and you might not be working the correct muscles. I recommend doing a quick search on YouTube after buying it to learn about the proper grip technique. Before I bought it, I thought it would help with my pinky, but surprisingly, my pinky turned out to be stronger than I expected. Interestingly, I noticed significant benefits for my ring finger instead. Slow and steady, and if you keep at it regularly, I'm not sure you'd even need to upgrade to the higher models. My index and middle fingers are already a piece of cake, so if I ever become obsessed with them and want to work them out more, I might consider upgrading to the red one, but I’m not sure I'd even need that.
Qualitywise, it's better than I expected. The springs are thick, and the middle segment feels more durable compared to the plastic on the finger section. If you’re particularly sensitive about plastic materials, you might want to consider the Pro model, but in my opinion, that would be overkill.