This is an attractive knob that can be used with M8 Bolts or M8 Nuts. I also included the Fusion-file in case you want to make any changes.
Print it upright - no supports needed
Also check out my M6-Version of this knob:

M6 Knob for Bolts and Nuts:
https://www.printables.com/model/1157934-m6-knob-for-bolts-or-nuts
The author marked this model as their own original creation.