what different of fine, medium, heavy, king, and Piont grades for clay bar? 
Fine:  fine clay bar, since 2006.  
it clean the comtaminants quickly,and deeply. 
the hand feeling a little bit hard. 

medium:  it is since 2009.   your purple is the medium.  
it is clean power and hand feeling also same as fine. 
but it is can use more times than fine.  and hand feeling also better than fine. 

Heavy:  it is since 2012 
it is different than fine and medium. 
this clay can use more times, more than 30 -40 cars (time) 
but the clean power is lighter than fine and medium.  

King:  since 2014  your red clay bar is King.
it is good performance.  
good clean pwoer and hand feeling.  
also can use more cars.  
what different with fine and medium?  the elements( powder) more finer. 

Piont:  since 2019. 
this clay bar has polish elements, it maybe hart paints. 
use fore deep deep corrosion.  or want to quick and qucik removal contaminants.