So you use them with tubs right? you place them underneath?
Yes I do.

Utratherm UTH do not get as warm as Zoo-med if left un-controlled by a thermostat however they still require a thermostat as the temps can still reach 105/110 if not controlled.

If you want to achieve proper temps you will need to place it underneath your enclosure (just take some substrate out), if placed on the side the UTH will not be efficient.