Countersinking is used to ensure that flat head screws or fasteners sit flush against the workpiece. JITTERBUG Pilot Countersink Cutters can be used with flush rivets in different countersinking applications. They consist cost effective alternatives to other brands. They are available separately or in convenient sets of different pilot diameters. Offered sets include 6 pieces (1/4 5/16 3/16 5/32 3/32 1/8 in.) or 4 pieces (3/16 5/32 3/32 1/8 in.) per set. For additional information please consult the supplied documentation or contact us.