Where would you normally use treated timber fence post caps ?
On top of a 70 x 70mm fence post to dress it up.

What is it made out of ?
Plantation grown Radiata Pine that has been H3 treated (suitable for above ground use).

How should you finish it?
A water based primer/undercoat is not a necessity (although it wouldn’t hurt), but at least 2 coats of the final colour is a must.
Leaving it unfinished, oiling it or using a clear lacquer is not recommended.
Speak to your local paint retailer for more info.