Upgrade your vehicle's ignition system with these Autolite 646 spark plugs. These performance/custom fit spark plugs are made of high-quality copper material with a 14mm thread diameter and a 21mm hex size. The spark plugs have a 12V voltage and are 3 inches in length with an installation depth of .708 inches. They are compatible with gasoline fuel type and are suitable for Eagle Vision, Buick Skyhawk, and Pontiac LeMans vehicles. In addition to the manufacturer part number 646, the spark plugs also have interchange part numbers 6729 and RN14PMC5, as well as OE/OEM part numbers 25164642 and 5613932. These spark plugs are not vintage parts and are made in the United States. Upgrade your vehicle's ignition system with these reliable Autolite spark plugs today. Exact item set is shown. New old stock spark plugs with original packaging in fair condition. Made in USA. No returns on installed items or partial sets. Please review our business policies in our store for information regarding returns, shipping and warranties.