PANEL DOOR BIT - The TPD 1 B 1/2 and TPD 2 1/2 are manufactured as matched sets in order that the rail and stile fit together as perfect joints. The TPD 1 B 1/2 now has a ball bearing guide ensuring simpler set ups for professional results. Arches on your cupboard doors are now much easier to achieve. Carbide Tipped, Two Flutes, Two Bit Set, 1/2" Shank, Wood Thickness - Min.: 20mm, Max.: 25mm.