Description and high quality. The drip can increase the oxygen in water. A trickling filter is a type of wastewater treatment system. Provides a large surface area for beneficial colonies to grow. Anti overflow baffle design, pores evenly distributed at the bottom of the box. Features - Color: Black. - Material: Acrylic - Size: 17.00X13.00X7.00cm/6.68X5.11X2.75in - and high quality. - The drip can increase the oxygen in water. - A trickling filter is a type of wastewater treatment system. - Provides a large surface area for beneficial colonies to grow. - Anti overflow baffle design, pores evenly distributed at the bottom of the box. - Stackable, use with aquarium gutter rack and placed on of the aquarium. - Warm Tip: Dear buyer, Due to lighting effect, monitor's brightness, manual measurement and etc, there could be some slight differences in the color and size between the photo and the actual item. sincerely hope that you can understand! Thank you!Package list: 1 set of filter box