The RIPP Pre-Filter is a specially designed filter wrap made to help extend the service interval of your washable air filter when used in very dusty conditions and provides a level of protection against moisture. They are made from durable polyester material containing uniform micron openings. The Pre-Filter will stop small dirt particles, and also keep the air filter element dry when splashed with water - yet add very little restriction to the air filter. Durable double stitching will make sure the Pre-Filter will stay in place.