dyed in the wool

/dˈaɪd ɪnðə wˈʊl/

dyed in the wool

having firm, unchanging opinions, beliefs, or ideas

Examples

1. So he's a very dyed in the wool deep learning researcher.

2. So you weren't a Disney guy, like dyed in the wool.

3. I'm a dyed in the wool theatre person.

4. But the point being is that demographics are pretty much dyed in the wool right now.