The secret to the Nealey Tire Repair Kit is the repair strand designed to last for years. The Nealey Tire Repair Kit repair strand is a cord consisting of uncured butyl and silicone rubber products that cure into the puncture, plugging the hole and forming a seal on both the inside and outside of the tire. For 2 & 4 ply tubeless tires. WARNING: Cancer and Reproductive Harm - www.p65warnings.ca.gov This warning is being provided to comply with the State of California's Proposition 65.