O Flute Router bit - 1/4” Shank (1/4" Cutting Diameter) - Amazon.com
CNC Plastic Cutting Router Bits - Down-Cut Spiral O Flute
Astra Coated Bits&Bits "O Flute" CNC Spiral CNC Bit
5mm X 20mm Up-Spiral O-flute Router Bit | Shaper Store
Amazon.com: SpeTool Single Flute (O Flute) Spiral End Mill Aluminum Cutter Carbide Router 1 inch Cutting Length with 1/4Inch Shank for Aluminum Acrylic PVC MDF Plastic : Industrial & Scientific