IRWIN Tools MARATHON Carbide Cordless Circular Saw Blade, 6 1/2-inch, 18T (24020) Silicone coat allows the blade to slice easier through material reducing pitch and resin buildup when cutting pressure-treated lumber. Construction-grade carbide teeth deliver longer blade life. Every other tooth is thinner for faster cuts. The innovative heat vent/expansion slot design reduces vibration for longer life and straighter cuts. Plate is fully hardened to run truer, longer. 18 tooth count blades are best for use with medium-thickness metals.