Duct Cleaning Brushes are designed and manufactured for duct cleaning where vigorous scrubbing action is not required. An excellent accessory for your duct cleaning system the floppy nylon bristles provide for gentle action to dislodge buildup and allow your big duct cleaning vac to remove it effectively. Duct cleaning brushes are made with .375in pipe threads for use with heavy-duty 60F fiberglass rods or 59F professional duty black rods. They can also be adapted to the ProFlex or LockFast Poly Rods. Due to the flexibility of the bristles we recommend you oversize when cleaning. Measures 24 inches. Brush only rod not included.