New type of floating or moving bio media. Also suited for trickle filters. Ø17 mm, height 17 mm. Surface area 720 m²/m³. Protected surface area is 589m²/m³ ! Because of the high protected surface area this media offers a very high biological filtration compared to other bio rings. Colour: white. On the displayed picture you can see the difference between new (white) biorings and "matured" bio rings with biofilm (darker colour).