One of the most important features of most of our spark plugs is the U-groove ground electrode. DENSO's patented U-groove spark plugs enable complete combustion by allowing the spark to fill the gap created by the 'U' shape. The ball of fire created in the U-groove develops a larger and hotter flame front that virtually eliminates excessive fouling and erratic starts by poor fuel mixtures. The U-groove is located on the ground electrode because this is the place that is least affected by wear. Thus we ensure that the benefits of the U-groove last the entire lifetime of the spark plug.

U-Groove is indicated by the "U" in the typecode

Example: K16R-U11, W20EPR-U