Diablo's, 3-1/2", Starlock Bi-Metal Oscillating Insulation Blades Feature Application Specific Designs That Deliver Maximum Durability And Longer Life When Cutting Insulation. These High-Performance Blades Feature An Ultra-Hardened Cutting Edge To Deliver Up To 5X Longer Life Than Standard Blades. The Serrated Blade Provides Faster, Cleaner Cuts In Insulation. Curve Contact Edge Creates A Pilot For Precise, Clean Plunge Cuts With Less Vibration. Tool Free Quick-Change Interface Fits Fein And Other Starlock Tools; Also Compatible With Most Non-Starlock Multi-Tools.