Made of advanced PET materials, standard pure 304 stainless steel core will not rust. Can suspended substances in water on a area, and the growth of nitrifying , swallow harmful , thus achieving biological and filtration effect The air, water and biofilm can be fully mixed and infiltrated to exchange, reduce noise, and disperse the momentum of water . Biofilm can not only implant evenly on each silk strip, maintain good activity and interspace variability, also gain more and more surface area in the process of operation, and have a good metabolism. Product name:Fish tank aquarium filter brush Type: fish size: 40x12cm Material:PET+stainless steel colour:black Package Contents: 10 x filter brushes Only the above package content, other are not included. Note: Light reflection and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.