Fabric Insert, 6mm Filter, is for the 6mm filter (not supplied) for use with 30 ltr & 47 ltr tanks. It is inserted inside the tank once the 6mm pipe is pushed through the 6mm Top Hat Grommet at the bottom of the tank.
It can be easily serviced and will float to the top if it comes detached from the tube; this will not happen if you make sure you have pushed the filter firmly into the tube.