The Makita B-66818 Impact Black Screw Guide is a magnetic screw guide with 1/4\" hex shank and a black coating to prevent rusting and corrosion suitable for applications including screwdriving joinery assembly fixings and more for use with Impact Drivers. The B-66818 has a higher durability with a longer life than standard bits and works well with both 25mm and 50mm Impact Black screw bits. The B-66818 works well with both 25mm and 50mm Impact Black screw bits (not included)