Reducer - equal and offset - INTERSECTION of cone with a plane

 
     The section is elliptical in most cases.                                                       
          In case of plane perpendicular to the axis, the section is a circumference.
  Technical description

 
   

  1. The plane closes an unspecified angle with the axis
     of the cylinder. 
   2. You can have either an unfold or section 
      or both of them.