Durable stainless steel abrasive bore brushes1⁄4 hex shankuse on ports, tubes, bearings and other common wire brush applicationsdo not exceed 600 rpmdo not turn counterclockwisedurable, abrasive, 6-piece bore brushes set features the most common sizes for cleaning tubes, ports, bearings and other general wire brush applications. stainless steel twisted wire gives it extra strength to increase cleaning action. each brush is fitted with a hex shaft for use with a standard driver. do not exceed 600 rpm these brushes are meant for push and pull use. never turn counter clockwise.