If you are doing a lot of wet weather riding the Internally Mounted Rain Sock is a good option. While not a necessity for riding in the rain with a RSD Air Cleaner, it can help reduce filter saturation. It installs under the air cleanr cover. Made from durable polyester, treated using a proprietary hydrophobic process to repel water. Uniform micron openings allows air in while keeping debris and water out. Dyno & flow bench proven to maintain current performance.