Water Resistant: Filter cover Hydrophobic treatment helps repel moisture and protect against water entering the engine due to puddle splash or heavy rainstorms. Although our Pre-Filters are proven to be extremely effective in repelling water, please keep in mind they are NOT WATER PROOF. If submerged, your intake can hold or pass water. This treatment will last for six months to one year, depending on use and conditions. As a general guideline we recommend replacing your Outerwears air filter cover with every other air filter service to help maintain its intended performance benefits. A quick test can help determine if it is time to change your Pre-Filter. Simply take an ordinary clean spray bottle filled with water and gently spray the Pre-Filter. If water beads off the Pre-Filter, your water repellency is still working. If you see water enter through the Pre-Filter, it is time to purchase a new cover. - - Maintenance & Cleaning - Depending on driving conditions, service intervals may vary. We recommend making a visual inspection as often as you would normally service your vehicle. If your vehicle sees a lot of dirt track competition (pulling/dirt drags) or dirt road driving, we recommend viewing the Pre-Filter at least after every race or trip. If you see a significant amount of dirt, you should clean the Pre-Filter. If the only driving you experience is street, we recommend checking the Pre-Filter every 3,000-5,000 miles. Although your Pre-filter may not require a thorough cleaning, you may want to shake off excess dirt to maintain your optimum horsepower and fuel efficiency, then reinstall. Caked debris can be loosened by soaking this filter cover, after being removed from your main filter and vehicle, in a mild soapy water solution and then rinsed clean and allowed to dry before re-installation. Do not scrub or use aggressive cleaning chemicals as the pre-filter and hydrophobic treatment can become damaged resulting in reduced efficiency and premature failure.