Rutland Products 16506 6-Inch Square Chimney Cleaning Brush - Heavy Duty Fireplace Soot Remover for Wood Stove & Fireplace Maintenance - Perfect for Homeowners & Professional Chimney Sweeps

After an exchange-for-size, I suggest to do-it-yourselfers that you order -below- the interior flue size to allow for movement of brush in both directions. The wire bristles are nice and stiff, and don't want to switch directions in a tight space when already bent even slightly one direction. Even going forward through even a slightly smaller space is difficult to impossible when pushing with the long segmented handles. Even if it 'just fits', it will be difficult to move back and forth. Fortunately, I had a rope tied to the bottom-side, dropped down the chimney to a friend, so I had no concern about it getting stuck when the extended fiberglass rods didn't want to push it through.