Unfortunately the only way to find out is to pick up the racket and play with it.

My concern now is there are so many racket manufacturers who have their own stiffness standard like stiff, extra stiff, flex, medium flex, etc. and sometimes they categorized differently.

Bottom line, my question is there any standard stiffness racket shaft that can be used as reference by players in case they want to use a new racket form certain brand to other brands…

Thanks,