Onsrud 55-000 series - 4 Edge Upcut Spiral - Solid Carbide
Available from Hartlauer Bits
This is an older series and has been used to cut a variety of different materials. It has always been a good choice when cutting more abrasive materials like steel and fiberglass. The multiple flutes leave a smooth finish and good life when an appropriate feed rate is used. These are also available with either a TiN or AlTiN coating for even better life.