Choosing the right grommet is requiring 3 basic dimensions. Your cable diameter, the diameter of the panel hole and the panel thickness.
FH dimension = panel hole size
H2 dimension = panel thickness
D dimension = the hole size of the cable grommet, depending on the diameter of the cable to be passed through it
Two complementary parameters are the H dimension (height) and the OD dimension (outer diameter), which describe the overall size of the cable grommet.