These dial indicator knobs feature an easy-to-hold knurled grip and are segmented into 9 gradations. The red short hand and black long hand allow for precise reading of the number of revolutions. Choose between a clockwise or counterclockwise rotative direction of the hands. Knobs have a reamed hole in the hub for direct mounting onto a machine spindle. Installs easily by tightening the setscrew. The knob and dial are made from aluminum. The window is made from acrylic plastic.