Galvanized Coupler Lock Pin – 5/16″Square coupler pins add an additional level of security preventing accidental uncoupling while in transit to better protect your trailer. Electrogalvanized steel construction for corrosion resistance. The snap lock bale is spring tensioned for stronger holding power. Fits most coupler sizes.WARNING: This product can expose you to chemicals which are known to the State of California to cause cancer, birth defects or other reproductive harm. For more information go to P65Warnings.ca.gov.