I ask because I've acquired this:
It's an electric control panel for a hot tub / spa with an 4000W 240V heat tube attached.
It's 15" long:
2.75" in diameter:
With a temperature senor attached on the outside:
It also has a pressure / flow sensor that I think it uses to ensure water is flowing through the tube before turning the heating element on:
Here's the inside. It needs a good cleaning:
Here are the electronics: