GREAT DESIGN: The sponge is designed and constructed with multi-layered principle, to provide larger surface area without clogging. Filters are designed and built for quiet operation. FIT FOR: Mostly suitable for external filtration system or above for pre-filtration purposes. FUNCTION: Sponge filters provide both mechanical and biological filtration. SUITABLE: do not trap fish fry. filter suitable in breeding season and spawning discus, dwarf cichlids, guppies and killifish. QUALITY ASSURANCE: To provide you with the highest quality assurance, if you are not satisfied with the product, please contact us. Product Description: Features: Model: 2831 double heads. The color black. Material: plastic + biochemical sponge. Features: 1>. The sponge is designed and constructed with the multi-layered principle, provide more surface area without clogging. 2> Filters are designed and built for quiet operation. 3>. Adapts to an external filtration system or higher for pre-filtration purposes. 4> .Provide better aquarium biofiltration system.Filters. 5> .Sponge provide mechanical and biological filtration 6>. Do not trap the fry. Filter suitable for breeding and spawning discus, dwarf cichlids, guppies and killifish. Package includes: 1x double head aquarium filter. Note: 1> .Please allow 1-2cm error due to manual measurement. Thank you for your understanding. 2>. Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.