This kit is required when installing L.E.D. lights as turn signals on a motorcycle with a single turn signal indicator light. If this diode kit is not installed, power will back feed across the indicator light and all turn signals will flash at once. Diode Kit Metric Bikes w/Single Turn Signal WARNING: Cancer and Reproductive Harm - www.p65warnings.ca.gov This warning is being provided to comply with the State of California's Proposition 65.