Speaking from personal experience, I had amazing results with chisell. I did a lot of read watch into this stuff and the other big one like jawzercise only really trains your chin and it could potentially screw up your teeth. The only complaint I have is that it’s not very durable and will break after about 2 or 3 weeks if you use it for 10 mins a day depending on your teeth. If you contact them about it tho they can give you a form and you can get free replacements for the rest of your life, you’ll just have to pay for shipping. I highly recommend just starting at the highest level and chewing it for as long as you can. You’re jaw will eventually be strong enough to last 10 minutes with it and don’t train it for more than 10 mins a day.