Low Helix, Downcut, Finisher, Spiral Router Bits - (3 Flute) Solid Carbide - Vortex 4550. Cutting Edge Diameter 1/2 Cutting Edge Length 1 1/4 Shank Diameter 1/2 Overall Length 3 1/2. The combination of the low helix angle and flute geometry make these tools razor sharp. They are recommended for acrylic, phenolics, UHMW, solid surface and dense hardwoods as a super finishing tool. The three flute geometry provides faster feed rate capability, while producing ultra smooth finishes.