UTH's are ok as long as you use a reliable thermostat (I prefer proportional) or rheostat. If you're looking for an inexpensive UTH check out the ultratherm uth sold at Reptile Basics. I have flexwatt in my rack, but I have a couple of snakes in quarantine and use the ultratherm uth's controlled by my t-stat. The ultratherms claim to not need a t-stat, but I still use one to be safe.