This was purchased for my 11 year old for Lacrosse after trying and failing at molding two traditional boil and fit mouth gaurds. From past experience with martial arts we know he's a chewer, so we wanted something that was a durable but comfortable.Over all the fit is good, it seemed a little small out of the package, but we followed the microwave instructions and once fitted the size was perfect.So why four stars? the strap, it's heavy duty and fully attached, exactly what we wanted, however it is not adjustable, it has one slot to feed the end through. Since it's fairly rigid attaching it to the mask of our son's helmet it was awkward and pushed on his teeth. After bending and moving it around several times we forced it to wrap around a bar so it rest in a better position for him to use.Overall good product, he's been using it for about two months, it has a little wear from his teeth, but still holding up well.If you know how to boil a mouthpiece and follow the instructions, this is one of the best mouthpieces that have given an excellent mold of my son's teeth. This was purchased primary because it was supposed to be "chew resistant." It does seem to be a better material and has held up longer than standard mouthpieces. However, don't expect it to last through the season if your child is a "chewer."My 9 year old really likes this mouth guard. He tried a couple of others for lacrosse before settling on this one. This one molded nicely and he got a good fit, and he's still able to talk and breathe and drink water with it in, so he's more likely to leave it in. And leaving it in is the only way for it to work! :)Oh, and we have bought this in the past, and it's easy to re-mold if you need to make changes, which is really nice.This is a decent product. When we melted for my son- the 1 side didn't form to teeth correctly. Not sure if it's user error- or just the product forming too soon after being heated. We've had a lot of mouth guards and it only happened with this brand.I purchased this for my 16 year old football player. I needed to buy him one with a stop as he has lost 3 previous ones that don't have them. This one fits well, is easy to mold and looks great too. It's a higher quality than some of the previous ones I have purchased. Most importantly he has not lost it, and it has stayed attached to his helmet!I was hesitant to purchase because I always bought the Shock Doctor mouth guards. What a nice surprise that these seem to be a bit more durable and my child does not chew them to nothing.My son likes it so far. My son loves Under Armour so he was just a little disappointed that the Under Armour logo came off so quickly. Only used it one day.Works as expected. Just be carefull when molding onto teeth. My son bit through the side.