JJC CL-F5K is the supplementary Filter Cloth of CL-DF1 Series Dust-free Air Blower. There are 5 pieces Filter Cloth in one set. Each Filter Cloth is vacuum packed to make sure it is clean and dust-free. The Filter Cloth is suggested to be replaced every 2-3 months, in order to ensure the air blower in its best working condition. If you are in dusty area, you can change it once a month.