Milwaukee HollowCore Magnetic Nut Drivers feature a thread-thru design for unlimited depth in threaded rod and long bolt applications. The magnetic universal driver heads fit 4X more fasteners including: Square. Hex. 12 point & Spline. Designed for maximum durability the Wrench Ready hex steel shanks are forged and chrome plated. Milwaukee Nut Drivers are designed for the jobsite and include Milwaukee's Limited Lifetime Warranty.