This is a dual action brush (compatible product) for iRobot Roomba 800 and 900 series. ● Replacement frequency: Recommended replacement is every 6 months to 1 year. *May vary depending on usage frequency and environment. ● Compatible models: iRobot, Roomba (800/900 series) 870, 871, 875, 876, 878, 880, 885, 890, 891, 892, 893 960, 961, 980, 985, etc. ● Quantity: 2 brushes (black x 1, gray x 1) ● Size: Length 18.5cm Diameter 2.5cm *Slight variations may occur ● Replacement method: ① Push the lever on the frame inward and lift it up. ② Remove the old aero brush. ③ Attach the new aero brush, matching the color and shape of the illustration drawn on the main unit. ④ Close the frame and you're done. ● Shipping: Ships same day. ● Packaging: Will be placed in a plastic bag and sent in an envelope. ● Other: As this is a compatible product, the construction may be slightly rough compared to the genuine product. Please understand the above before purchasing.