Pellicle Series Needle Felt Filter bag Needled felt is the most common media used in economic disposable bag filters. Its fibres are locked together when they pass through beds of special barbed needles, entangling them into a strong matrix. The down stream side is signed using a special heat process to eliminate fiber migration. This rugged media is ideal for fabrication by both sewing and welding.Available in a wide range of materials, needled feits can be used in a vast range of liquids and gases of low to medium viscosity. They can be applied to remove hard partcles or, in some cases, soft partcles and jels. Kfilter offers needled felts in PO, PE, PA and PTFE in the full range of bag sizes.