Did you know that we have 2 different types of weldon flats? It's true! We have a Standard Weldon Flat and an Advanced Performance Weldon Flat. The Advanced Performance Weldon Flat and the Standard Weldon Flat are essentially the same, but the length of the Weldon Flat to the cutting end of the tool is different. The Advanced Performance Weldon Flat is measured from the flute washout to the flat. This guarantees that the flute or flute washout will not be inside of the holder. If the flute or flute washout is inside the tool holder, the chips can pack into the holder and can cause the tool to break.