This is my first post on this forum.I find that the vast majority on here are very informative.I have kept pythons and boas for 15 years.I now only have two Ball Pythons(normal=female,pastel=male).Anyway I saw this posted and thought I would chim in.I believe that hot rocks with a rheostat are fine as long as the surface temperature does not feel too hot on the back of your hand.I let them sit outside the cage for 24hrs AFTER I have found the the desired temperature.If after 24hrs it feels the same then I place it in the cage and check it the next day again to be sure.I have never had any problems with hot rocks.This is just my 2 cents.I am not trying to have anyone replace what they use byreading this.I just wanted to let others know that they MUST be cautious with these.I would never use one without a rheostat.