The Lenox 12" x 6 TPI Titanium Nitride Coated Wood & Metal Recip Blades (5 Pack) (21061-156G) have a specially formulated Titanium edge which improves the wear resistance of the teeth for faster cuts through the blade's life. The bi-metal technology flexes, resists breaking and also extends the life of the blade. The reinforced tooth design and Titanium coating combine to create the longest lasting blade, ever.