West System 404 High-Density filler is the most cost-effective and easiest-to-use filler for hardware/stud bonding. Blended with epoxy, it makes an excellent gap filler or structural fillets. Can blend it into any West System 105 Resin/Hardener combination, G/flex Epoxy 650, or G/5 Five-Minute Adhesive. Cures to an off-white color.