Dont make the mistake of thinking Delrin is merely a trade name for acetal.....it isnt.
The acetal produced by Du Pont and called Delrin is much better than regular acetal....it is also more expensive.
If you can get Delrin get it.
I have never quite understood why all tuners use white, when Black has exactly the same characteristics and looks much better down inside cocking slots.
Jury is out for me at the moment in regard of top hats and guide rods though...
I have discovered some quite eye opening issues .....but its ideal for these piston bearings if you can manage to glue them in correctly.