MECHANICAL FILTRATION: The use of filters socks IMPROVES WATER QUALITY by trapping debris, detritus, excess food, sand, coral and more HIGH QUALITY PROFESSIONAL GRADE: These filter socks are designed to be sturdy, strong, and heavy duty to be RE-USABLE and cleaned WATER: These 200 Micrometre felt filter socks trap smaller matter and debris that larger or mesh filter socks do not catch to water REDUCES NOISE AND SPLASH in your aquarium/pond overflow system colour: white Material: polypropylene PP size: diameter 105mm; overall length 380mm Package Contents: 4*aquarium filter 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.