Why Do NGK Plugs Have Two Numbers?

Many spark plug brands, including NGK, have two different ID numbers assigned to spark plugs - a 3-5 digit stock number and a longer alphanumeric part number.

The alphanumeric part number identifies the spark plugs specifications and is printed on both the spark plug and the box.

The stock number is used by distributors and retailers to aid in stock management, as the alphanumberic number would be difficult to manage inventory by. This number is found only on the box and has no relation to the spark plugs features or dimensions.

NGK products can be found and purchased on NGK.com using either number.

See NGK's numbering system for assistance in decoding an alphanumeric part number.