properties /measurement

The distance the spark has to jump between the centre and ground electrodes, as a length. Published as a named column by every maker — NGK heads it "Spark gap" and encodes it in the part-number suffix (-7 = 0.7 mm, -9 = 0.9, -10 = 1.0, -11 = 1.1, -13 = 1.3, -15 = 1.5), which is why so much of the trade's stock ends in -11; Denso publishes 1.1 mm for the IK20 and the SK20 range; Champion publishes `0.029-0.035 in (0.74-0.89 mm)` for the RN9YC. Modern iridium and platinum plugs are shipped pre-gapped and must not be bent, which is exactly why the figure has to be on the shelf record rather than left to the fitter. NOTE the Champion case shows the figure is sometimes published as a RANGE and this grammar can only hold a point — the pool-wide bound-and-range gap first written up as H2-f1, recurring here.