The P6419/P68xx probe manuals mention a thick and a thin PCB. How do I know which one I have?

The P6419/P68xx probe manuals mention a thick and a thin PCB. How do I know which one I have?

If the PCB thickness is 1.27 mm to 2.36 mm (0.050 in to 0.093 in), use the nut bar with the thin elastomer.
If the PCB thickness is 2.36 mm to 3.81 mm (0.093 in to 0.150 in), use the
press-in nut with the thick elastomer.