Honestly I just came upon this randomly. Figured I'd give it a try. I'm not so much a gym junkie but rather a firearm nut. So I wanted to improve grip strength. I tested all of them because I didn't know which one was what. I closed all of them and figured it out... then saw the numbers on the bottom of the grip handles. Not the brightest man. But I digress, the green and blue weren't great to start with so I went the silver. After the first day I couldn't sleep. It felt like my hands were runover and then backed over. Then the next day or 2 I was closing them like there was nothing in my hand at all. I thought this cheap junk, I couldn't have improved in such short time they obviously lost tension. They also are doing this weird squeaky noise, the coils are starting to rub. So I handed them off to someone else and they couldn't close them. So maybe they're not entirely useless. I am going to do high reps with the silvers and then move onto greens. But honestly it took like 3 or 4 days and I already see alot of vascularity on the insides of both of my wrists. So if you're a depressed edgy kid probably don't buy these, makes the job too easy. I can also see a vein going down the middle of each forearm. Which I couldn't see prior. It's not really popping out per say but it's alot more visible. As in I can actually see it through my skin now. I am decently strong but I am lazy, so I don't work out like I should. So don't expect to be noodly and have the same result. But this does work. I also do holds for a minute or 2. Those really start to get to you.
Will definitely buy more once I close the blues with ease.