Collector spark plug WATTERS ALL SPARK. Used. 7/8"18.Some pitting see photo. Very odd bottom. Correct top nut, size 3/4" tall. Buyer to pay shipping and handling, to be determined at auctions end. Payment must be recieved within one week of auctions end or neg. WE DO NOT ACCEPT PAYPAL. Feedback left and ebay contacted. If you have any questions please feel free to contact me. Thanks and good luck.