I always take a shot down the clay tile liner to check for creosote and blockages but found this when goiung through my pictures.
Roof material and Chimney brick were enough to hold my attention that it slipped my noticing what at first looked like a blockage and then a brick configuration.
Perhaps to support the liner from the roof line up but it seems like a big reduction at inner dimension.
Am I off base to be concerned, as this is a standard HVAC ,Hot water tank hookup.?
1,400 sq ft brick home.