Works as advertised. I use it for striking and mma and it is a huge step up from conventional mouthguards. You can keep your jaw clenched and still breathe through your mouth. It's kind of bulky but totally worth it. You get used to the bulk after a few uses. It doesn't form fit super well with boiling, but if it form fit to well the breathing channels would probably get crushed. I'd use it for a few weeks before even trying to boil or fit it, and then maybe boil and fit, unless you have a really uneven or weird bite, then boil away. I'd also get a cheap small one that is more comfortable for BJJ or grappling as you don't need to keep your jaw clenched the whole time training unless striking is involved.