So I've got the ram air set up (RLR) off a previously running bike ready to plop onto my race NC30. But I feel like it needs an air filter for protection other than the chain lube sprayed inside the airbox.
What do you guys use?
Wire mesh or an air filter? And where do you mount it?

Most people bend a piece of mesh into a U shape
and pop rivet it in a few inches into the intake snorkel.
Keeps stones etc out

I've heard of people using the wire mesh off the stock air filter and putting it in between in the joins on the duct

I used a sheet of this (as Rhory says) between the scoop and lid joint, then chain cleaner on the baffel plate to catch any bugs/dust.

This is how i run my HRC open carbs