Whiteside 13-1000 Helix Mortise Bit w/ Downshear 1"CD, 1/2"CLWhiteside 13 1000 Helix Mortise Bit w Downshear 1"CD, 1 2"CL Product Description These Mortise heads are designed to screw down onto a Helix Mortise Arbor (Part #HMA 1 4 or #HMA 1 2) for easy transition from one cutting head to the next. The Mortise head is only available with a downshear cutter. Materials: Natural woods, composite woods, hard plastics Recommended RPM: 12,000 14,000 (max 24,000)