I have used zoo-med, exoterra, and Ultratherm UTH's. I like the Ultratherm because it does not have a sticky side, you just sit it underneath the tub. Most people on this site will advise the use of flex-watt. I have never used it, but have only heard wonderful things about it...see Matt @ mg reptiles, he'll help. You will also hear people tell you that you need to get a thermostat. All UTH's need to be run on a thermostat or lamp dimmer. I can tell you that I resisted spending the money for way too long....I used a lamp dimmer, and had to adjust it several times per day, and I was always worried about my temps. Everyone here is right when they suggest purchasing a t-stat...it is worth every penny! (again, Matt at MG).