Just saw a "Drum Heater"... Is this just a giant Flexible Heater?

I was browsing for thermal solutions today and stumbled upon something called a Drum Heater. It’s basically a massive jacket or belt you wrap around those big 55-gallon oil drums to keep the liquid inside from freezing or thickening.

It looked surprisingly familiar... is it just a giant-sized version of the Flexible Heaters we've been talking about lately? Or is there some secret industrial tech inside those big belts?