Yes the Q factor. I’m 5.8 with long legs. q16 is ok but if you have wide hips and can ride a 170mm arm I think they even go higher the q16.
Got these last week for my bike. Tried a few. My wife has the delta on hers
Kies Cranks 160 Q:16 Isis Cold-forged aluminium alloy Black Granite for E-BIKE