WEST SYSTEM 403 MICROFIBERS ADHESIVE FILLERS - 403 Microfibers, a fine fiber blend, is used as a thickening additive with resin/hardener to create a multi-purpose adhesive, especially for bonding wood. Epoxy thickened with microfibers has good gap-filling qualities while retaining excellent wetting/penetrating capability. Color: off-white. Sold by the 6 oz. Can, 20 oz. Can or 20 lb. Bag.