These spiral bits offer state-of-the-art results in flush trimming. Made from solid carbide, each bit contains up-cut and down-cut flutes and is tipped with a double ball-bearing guide. This flute design creates a compression cut that prevents fraying and splintering. Compression spirals will save you time and money on finishing your project's edges by reducing sanding time. The Ultimate Flush Trim Bits for material up to 2-1/8" thick. These bits provide the performance and quality of the Classic Ultimate Bits on thicker stock. For best performance, use the shortest cut length needed for the application. Whiteside Machine Company has been in the router bit business for over 30 years providing customers with quality products while at the same time striving to achieve complete customer.