Series A940 HSCo High Helix (Parabolic Flute) PFX Straight Shank Long Series Drills Metric. Excellent performance across a wide range of materials. Parabolic flute design promotes constant chip flow. High productivity "one-hit" drilling to 10xD. Bright finish. Size Range: 1.0 - 20.0mm, 3/64" - 25/32". This drill bit is part of the A940 series, features HSCo High Helix with a Parabolic Flute design for optimal chip flow, and is a straight shank long series drill with a bright finish.