This is the Bio-Wheel replacement assembly for the Penguin 170. The Bio-Wheel bracket is sold separately. Delivers a classic wet/dry biological filtration. OVERALL DIMENSIONS 5 IN. X 2 IN. Delivers a classic wet/dry biological filtration. Because the wheel is only exposed to prefiltered water they do not clog, and never need to be replaced. Eliminates toxic ammonia, create higher oxygen levels & a stable ph, and a healthier environment.