These are the clay flue tiles prior to installation.  They are lowered into the chimney one at a time, placed on top of each other and joined together with a mortar sand mix.  These are 8"x12" outside diameter and are 2' in height.  In this case each flue needs to be raised approximately 6' to meet current codes.  To see the chimney before http://www.dmstorrschimney.com/our-soot-stories/adding-clay-flue-tiles-in-belmont