Red Sea Reefer Filter Media Cup can be used with all Reefer sump filter holders. This cup can easily be filled with a wide variety of media types. Etc.. filter pads, filter floss, biological media, carbon and GFO.  Designed to be placed into the sock holder these cups can be used in place of the standard filter socks.
 
Fits all Reefer sump filter holders
size - 4" x 8" inchs
holds several types of media / used in place of the standard filter sock
Part# R42177