After suffering a small injury after a randori I decided to get a good mouthguard to prevent further injuries. After checking multiple sources (forums, blogs, etc.) I decided to buy this one and boy I was right!
The heat-and-mould process is straightforward as possible, 1"30 in hot water, 3s in cold water and then put it in the mouth to mould it against your teeth and gum.
Although it is a small one and covers only the upper teeth, it does its jobs perfectly by providing a solid protection. Since I bought it, I did a dozen randoris and twice it protected my teeth from an impact coming from my lower jaw.
You can even breath with it, I'm able to withstand full length randoris without having to take a breather between them. And yes, you can also drink with it, that's a huge plus!
I'll definitively buy another one if at some point it fails me, it's an impressive product with an even more impressive price.