I've got some that i take my Let. with. I don't know exactly what kind they are, but if you let the Let. stay in it for @ 30 min. without taking it you are screwed! I put one on my counter and came back to it in about 25-30 min. and it was melted down to nothing but liquid......I wish i could find some that you could just put the liquid in and not have to worry about this happening.