Made of premium plastic materials, these filter plates are designed with net grid structure and specially designed for fish tank use. With special and practical structure, they can be used together with some proper air pump, filter pump, submersible power head to increase the circulation and help with mechanical and chemical filtration. Features -Material: Plastic -The internal grid holes are less dense and effectively prevents the sand from leaking into the bottom of the fish tank. -These plastic grid filter plates can be cropped and free splice combination. -With stable and rationalized bottom design, it can be stably placed on the fish tank. -Carefully selected and safe materials will not cause any hurts to the . -Help circulate the water under gravel layer in order to reduce of gravel. Package list: 30 Tank Bottom Filters