Our 7" Filter Media Cup will replace all those filter socks you have hanging around. Made out of a BPA free Polypropylene, this 4" Filter Media Cup is a solid one piece design, that holds any filter media. The round design allows the Cup to slide into place, regardless of which "side" slides in first. Directions: Wipe cup with vinegar, then simply place Filter Media Cup into your filter tray, and fill with desired filter media. To clean just replace your filter media. No rinsing necessary.