The K&N Drycharger is a silicone treated, polyester wrap that is made to cover K&N Air Filters or Personal Watercraft Flame Arrestors. These Drychargers, which are similar to the K&N Prechargers, contain uniform micron sized openings that allow high air flow. Yet, due to the Drychargers silicone treated polyester wrap, the amount of water that reaches the air filter or flame arrestor is limited. This product wraps your air filter with an additional pre-filter Extends service interval of your K&N filter Durable silicone treated polyester material with stitched elastic openings Water repellent treatment typically lasts 1 to 2 years