The original Bondo hardener, Bondo cream hardener when mixed with Bondo 2-part Filler products, provides amazing, long-lasting automotive repairs.Bondo Cream Hardener mixes with Bondo 2-part fillers, putties and glazes to create high-quality, long-lasting repairs. When the filler and hardener are mixed, a chemical reaction occurs to create a mixture that will deliver a strong, lasting repair. Our hardener is smooth and easy to mix. Hardener must be used with Bondo Fillers and is not designed to use alone.