4" Pre Sump Filter Sock Holder(Mount) and Free Filter Socks 200 Micron,4 Inch Ring by 14 Inch Long -Aquarium Felt Filter Bags for Aquarium Reef Tank Micron Bag;

Filter Sock Holder-It is a simple filter .
Very simple and inexpensive way to add filtration to any of your 1" outlets such as overflows and skimmer outlets, front and back to fit and work in a wide range of versatile applications whether it's a tight sump or that stubborn pipe or electrical cord in the way.
The filter sock holders are designed to universally fit and work with mostly all sumps in the industry.