You are buying a Compatible Coarse foam filter pad suitable for the Juwel Jumbo / BioFlow 8.0 Filter. The blue course sponges contain the biological cultures, for biologically filtering your water. It is recommended to change the coarse foam pad every 3-6 months. These pads will fit the Juwel Jumbo / BioFlow 8.0 Filter: Rio 400, Vision 450