New ND Nippon Denso Hot U Racing Spark Plugs X31ES-GU

Up for sale is a New ND NipponDenso Hot U Racing Spark Plugs X31ES-GU. This plug number I used in my CB750F Race bike back in the 70s. This would be a very cold plug. (infineon, Sonoma Raceway). The boxes do not look so good but the plugs are new.