Our 4” Carbide Chain Knocker for the M18 FUEL™ High-Speed Chain Snake delivers a wall-to-wall clean that can tackle scale build-up, hard deposits, grease, and tough blockages. The carbide chain knockers are best used in Cast Iron and other hard-walled pipes. These carbide tabs deliver strength and durability for long-lasting descaling performance. These steel chain knockers feature durable construction to tackle tough clogs in 4” lines. Featuring stainless steel set screws for corrosion resistance. Additional accessories available for more descaling and breaking up grease: 1-1/2” Carbide (48-53-3024), 2” Carbide (48-53-3025), 3” Carbide (48-53-3026), Grease Penetrating Head (48-53-3028).