There are a lot of different UTH on the market. Some become excessively hot some not so. I don't recommending brands to do become super hot. The low density carbon heaters (ultratherm, intelliatemp, zilla so I understand, and exoterra RAINFOREST) they rarely become hotter than 100º and usually will not heat beyond 10-15º higher than ambient air temp. I would no advocate use with no thermostat but it adds a layer of safety if the pad will not get hot enough for permanent damage.