How to add second head unit/device? - to add additional power

Hi guys,

I have a Eonon double din head unit installed in my 08 forester and want to add an additional single din unit, for the additional power will I need a T harness adaptor like this to power the 2nd unit? Does this plug straight into the ISO cable and just provide additional power?

https://aerpro.com/ct10su01

Thanks