Racing Spark Plugs
NGK racing spark plugs are available in a variety of sizes and designs, most are now produced with Iridium centre electrodes, some have a solid platinum ground electrode and others (surface discharge types) have no ground electrode at all. Being a specialist product and involving a substantial investment we would assume that you will probably know the spec and possibly even the part number that you require. Not all plugs are available in all heat ranges.
Note that the last digit of an NGK racing spark plug number that begins with the letter 'R' (e.g. R1234-8, last digit is 8 in this case) denotes the heat range of the spark plug. The part number is not otherwise descriptive in any way, details of thread size, firing end design etc can only be found in NGK's race catalogue or from data we have supplied here.
For a cost effective alternative, consider a Denso Iridium Racing Spark plug, equivalents are available for most NGK part numbers and at a much lower price in many instances.