It's a rounded cable, instead of a flat tape.
Heat cables are sturdier than heat tape, but can be harder to install (you usually want to put it in a routered groove). They don't heat as large a surface area, but they get the job done.

I have Animal Plastics racks with heat cable, and they're great. I also have one now with FlexWatt. I don't know how it will be for durability, as I just got it.