When I buy a used machine, the air box is one of the first things I check. That can speak volumes regarding: Where the quad was ridden (dried mud or dust inside) and how the quad was taken care of (condition of the filter).

I agree with the Wolverine/Warrior guys...stock filter design is crappy. I replaced mine with a Noss intake with a K&N and an Outtwear.

The Outter wear (from what I understand) is watter repelant. Basically, if a bit of water makes it's way into the box, it should bead off the Otterwear. However, it's not water proof.