Denso Iridium Racing Spark Plug IWM01-29 / 5726 Replace 267700-1210 R5184-9.5Iridium Racing plugs are ideal for racing and tuned-up engines. Because racing engines do not have standard specifications it is important to select the appropriate plug type. Generally, electrodes that project into the combustion chamber have better ignitability and better performance. However, because of more exposure to high temperature combustion gases and as the ground electrode becomes longer, heat resistance and durability decrease. The higher the level of tuning, the greater the need to use a less projecting type. As the level of tuning increases, so does the need for a higher heat range.F1 technology Ultimate acceleration High reliability Boosted performanceDIMENSIONS: Height (mm): 30 Width (mm): 30 Length (mm): 90If you are unsure as to whether this is the correct part for your vehicle, please don\'t hesitate to contact us. Alternatively please use the cross reference table above.