When I bought the mat w/out dimmer the glass was VERY hot to the touch. I've only had dimmer on it for about a week now. I was constantly re adjusting this and that b/c my temps won't stay in one place. I checked temps this morning, kinda low so I upped the dimmer. Later this afternoon, not much change upped the dimmer. went to dimmer max. nothing! so I felt the glass on bottom is was cool, lifted the tank slightly and put my finger on mat, cold. so I unplugged everything. I plugged heat mat back in w/out dimmer this time and it's been plugged for about 2 hours and barely even warm to the touch. so I'm thinking it's shot. the store I got it from only sells the exo terra ones so I'll have to bite the $15 I spent on it and go to another store to get the zoo med.