Accord AOBBOL18 Oak Baseboard Register, 18-Inch(Duct Opening Measurement), Light Finish Solid oak construction; Premium stain and durable lacquer finish Color may vary slightly based on the underlying wood product For floor application; wood flap damper adjusts air flow Listed product sizes refer to the duct opening measurements, not the register itself Actual length of item is 18-inches; inside duct opening measurement of item is 15-inches to accommodate the 1  -inch wide flanges on each end