Barrel or cylinder

         Barrel or cylinfer            

  the rear side of reservoir barrel or cylinder stays 

his inside master cylinder and, inside of master cylinder  stays all.part is sitting       on the cylinder from the  reservoir  side stays two hole 

 Stays from the push rod side stays one hole 

  being  they hole is big 

   his Called  primary  port    

and second hole his called secondery port or by passed  port  or   Composting port also says 

When you do press brak pedal at the time first oil supply Does primary port 

 After leaving  The brak ,The oil  coming from wheel cylinder       from  by-pass port  return coming in reservoir