unknown device in service panel

Hi everyone,
What is this device in the service panel and what does it do?
Thanks.It is connected to both live services conductors and the neutral.

Lightning arrestor/surge protector.

Most manufacturers (Delta) tell you to install it inside the panel box (for safety), but on my house I installed it on the outside of my panel box so that I know if it has to be replaced. Plastic goo blows out the bottom if it takes a hit, something I might not notice to replace if it was inside the panel box.

Incorrectly installed Double taps

Yeah, but you’ll see them installed on the main lugs like that often.

Yes but that does not make it right.
Put in a breaker and feed the surge protector.

Some type of lighting/transient suppressor. Its not done to code, as neither are the lugs listed for two conductors nor can copper and aluminum mix like that.

Improperly installed surge suppressor …