Kuryakyn 9559 Pre Filter/Rain Sock Kuryakyn uses only K&N and aFe oiled gauze filters in their air cleaners which, when properly maintained, are water repellent. Even so, there may be times you wish you had a pre-filter to keep bugs, dirt, wash water, or torrential downpour out of your air cleaner.Pre-filter for Mach 2 and Alley Cat air cleaners.Water repellent, UV resistant and filters debris down to 0.005".Made by Outerwears.Note: Kuryakyn part number: 9559.