WEST SYSTEM 407 LOW-DENSITY FILLER – 407 Low-Density is a blended microballoon-based fairing filler for WEST SYSTEM Epoxy. Add 407 to a mixture of epoxy resin/hardener to create a fairing putty. It’s easy to sand or carve this putty once it has cured. Low-Density Fairing Filler filler is reasonably strong on a strength-to-weight basis. You can blend it into any WEST SYSTEM 105 Resin/20X Hardener combination, G/flex Epoxy 650, or G/5 Five-Minute Adhesive. Blended with epoxy, it will cure to a dark red/brown color. Sold by the 4 oz. can, 12 oz. can or 14 lb. bag.