36-47 Knucklehead, 52-73 Servi Car, 45-51 GL, 45-52 WL, 45, 49-52 WLA
Spark Plugs including a wider-base insulator which provides an easier path to speed the transfer of heat and a longer insulator nose containing a center electrode of pure copper inside of chrome-nickel to transfer heat between firings and help resist fouling.