Shoemaker 1600-10X18 10"x18" Floor Grille - Brown This product is designed to fit a 10" x 18" hole. Overall outside dimension is 12-3/8" x 20-3/8". Heavy-duty honeycomb construction; blades run parallel to longest dimension. Paint is a brown, driftwood tan finish. Flush core and frame provides smooth surface; Free area equals more than 75% of nominal size.