I also wanted to add an interesting find. I know someone said it works on glass, but in my experience it didn't just by laying it on the heatbed. I did find out however that putting aluminum tape on the back of the glass made it detect it and it is only off by about 2 or 3 mm compared to the regular bed. I also would think the aluminum bed to aluminum tape would conduct heat better if using it.
I also wanted to add an interesting find. I know someone said it works on glass, but in my experience it didn't just by laying it on the heatbed. I did find out however that putting aluminum tape on the back of the glass made it detect it and it is only off by about 2 or 3 mm compared to the regular bed. I also would think the aluminum bed to aluminum tape would conduct heat better if using it.