From what I've seen, APA falls under the URO parts umbrella.

What is left of the mast on my car is non magnetic so it looks like the aftermarket is a indoor style steel mast.

Still, in my case its $ 10 against $ 85, if a factory mast was $ 40 I would not even bother with the aftermarket.

My car is summer only, stored under a car port / in garage so rust is a long way out. I've seen antenna lube on the Hirshmann site, a bit of light oil might do the trick to prevent sticking and rust.