R25 51mm Threaded Button Bit for Rock Drilling The R25 51mm dome threaded button bit is a top hammer rock drilling tool designed for heavy-duty underground drifting, tunnelling and small-hole bench drilling in medium-to-hard rock. With a normal skirt body and a powerful 9-button configuration, this 2-inch rock bit delivers high impact resistance and exceptional gauge maintenance. Product Overview Engineered with six 10mm outer gauge buttons and three 9mm front buttons, the