What is a dual tray mouthguard?

[ThirteenTwo]

Was lookin' at this: Jaco Guardian Dual Tray Mouthguard

I did a little googlin' but I couldn't find a better explanation than what's on this site. Does it mean it's a mouth guard that you don't boil and bite and/or customize?

 

[El Arquitecto]

Yeh, you still have to boil and bite. The difference is that this has a slot where your bottom teeth go into aswell. Basically a double mouth guard, top AND bottom.

 

[hughes fan]

I train with a guy who has a double mouthguard and he says it's like training with a normal mouthguard.