Insert Bit Ecx 1/4"Hex, Milwaukee 48-32-4440, 2 Per Pack, 3 Pack. Our SHOCKWAVE ECX Impact Bits are engineered to be the Most Durable, Best Fitting driver bits on the market. The Wear Guard Tip delivers increased wear resistance which protects the fit over the life of the bit. The Shockzone is optimized for each tip type and length of driver bit to absorb peak torque and prevent breaking. The Custom Alloy76 has a customized steel and heat treatment per tip type to extend the life of the driver bits, providing up to 50X life vs. competitive impact driver bits. Wear Guard Tip protects fit over the life of the bit Custom Alloy76 Steel is engineered to extend bit life Shockzones are optimized in both length and width per tip type for best performance across tip types. Customized geometry and heat treatment per tip type for best performance across tip types Laser etched size for easy identification Optimized Shockzone absorbs peak torque and prevents breaking Precise Fit Custom Machined Tip prevents stripping and reduces wobble. Laser hardening at the tip creates an outer protective shield for improved wear resistance. Up to 50X Life vs other impact bits Designed for use with Impact Drivers and Drill Drivers