Heat Pads and Heat Rocks - Iguanas in their natural habitat are heated from above by the sun. And you should be able to create a properly heated basking area for your iguana to bask in, therefore not needing a heat rock. If you absolutely feel that your iguana wants to get belly warmth, or maybe you have been using a heat rock successfully for a long time and your iguana loves it, then get Zoo Med's heat pad and rheostat so that you can regulate how hot the pad gets. And never put your heat pad directly under your lights. It makes the pad much too hot.

rheostat

HEATROCKS BURN IGUANAS! DON'T USE THEM!