While browsing for injectors for a 12-valve firepump engine I noticed some ads like 5x.010-Cummins... 5x.014-Cummins... 5x.020 & 5x.030

What do these mean specs mean, orifice openings?

How are injectors classified and what would be the required injector specs for engine type Cumins 6BTA5.9-F1 (#45654340)?


TIA