Yes - sometimes they are black or cream but all do the same job. I use one and run it through a thermostat which you set at the required temperature and it switches the CHE on and off if the temps rise and falls - keeps temps even and safe.Like what grandpa turtle posted?
Apologies if I'm preaching to the converted or repeating another member but don't use any coiled, or long thin loop type cfl bulbs as these damage torts eyes. Torts are also confused/stressed by coloured lamps - especially red.