Features: Easy to install and use Effectively keep household dust. Made of high quality material, durable and practical to use Made of qualified material, it can contain small dust. It is recommended to change once every 3-6 months Applicable models:For N79 N79S 990 Colour: Black Material: PC+ metal Package includes: 1 * wheel Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.