You are buying a Compatible Fine foam filter pad suitable for the Juwel Standard / BioFlow 6.0 Filter. The blue fine sponges contain the biological cultures, for biologiccally filtering your water,a nd removing small particles from the water column. It is recommended to change the fine foam every 3-6 months. These pads will fit the Juwel Standard / BioFlow 6.0 Filter: Rio 240, Vision 260