I followed fitting instructions exactly and the 2 whole minutes in boiling water was bad enough to start ruining the black liner base, then after letting cool and biting/shaping the mold fit great around all my teeth BUT left the black base exposed badly in the inside middle/center portion. I let it set in ice water as recommended, then put the guard in and could feel the exposed black base pressing into my gums right at the inside center. I attempted doing basic drills because I did not trust the mouth guard for sparring. Sure enough, the mouth guard stayed in my mouth fine and I could breathe well, but within seconds I could feel it rubbing my gum raw and it left the part between the inside middle where my teeth/gums meet raw and starting to bleed. Very disappointed.
