asc6000

iTrader: (15)

The outer filter is larger "pores" to grab bigger stuff while allowing smaller particles to flow freely to the inner where the finer "pores" do their job. If you had one thick filter the outer being small pores would get clogged easily and quickly.

MotoGod

iTrader: (118)

For me it's added piece of mind. Both filters are the same density, so dual stage is semi useless anyway except for the fact tgat the top layer doesn't contact the inlet directly. It kind of overlaps the inner filter.

madweazl

iTrader: (12)

I see no point in not oiling both. On a dusty track, a dry outer provides almost nothing so why bother running it at all? There is no loss of performance running an oiled outer and it provides more protection to your investment. Additionally, it only takes a couple seconds to replace the outer. What I would like to see is a company that sells pre-oiled outers separately.

BPro

iTrader: (13)

+1

Pulse_

am I the only one who only oils the inner part of the outer filter but not the outer part?

to me it's the most logical, if you oil the outer filter totally it will catch dust on the outside because it sticks way more than a non treated foam