Jagg Oil Coolers JAG-4501 Oil Cooler Adaptor w/By-Pass for Harley-Davidson Air Cooled Milwaukee-Eight 18-UpBuilt for reliable performance and easy installation, the Jagg part # 4501 oil filter adapter allows for easy access to the oil supply while maintaining optimal flow characteristics. After filtration, the oil will by pass the oil cooler automatically while the engine warms up to standard operating temperature. Once the bike reaches operating temperature, the Viscosity Regulated Flow (VRF) valve will automatically close the #4501s by pass hole, sending