nsert bit holders magnetic with c-ring lgth 6 inches Use with Milwaukee Shockwave impact duty insert magnetic nut drivers. 2 piece construction withstands abuse in impact applications. Proprietary steel and heat treated process for maximum strength and durability. Powerful magnet allows for a secure grip an d unyielding bit engagement. For use with Insert magnetic nut drivers ( 1/4 inches, 5/16 inches, 3/8 inches, 7/16 inches and 1/2 inches ).