To avoid interference with radio frequencies, the manufacturers use so-called suppressed spark plug plugs and, if necessary, suppressed spark plugs. Caution applies here when using suppressed plugs: double is no better here, no spark suppressed, as the entire suppressor resistance would be too high.

For an easier overview here, a little legend for NGK spark plugs:
The letter combination before the heat value (number) gives information about thread diameter, hex key width and design of the spark plug.
The following number indicates the heat value.
The letter following the heat value indicates the thread length.
E = long thread, H = short thread.
The letter after thread identification contains data on special spark plug construction features.
The last position, in turn, a number, encrypts special electrode distances.

Some candles have a quite short combination. No specified is missing.

Here: a spark plug. If several are required, please order the corresponding quantity.