All Miyazawa key cups are made with a perfectly flat bottom surface, providing a more consistent surface on which the pads are seated.

Why is it important to have a key cup with a flat bottom?

For the most full and resonant tone, the pads of a flute must seal perfectly. To accomplish this and increase the stability of pad adjustments, Miyazawa key cups are milled from a solid piece of metal to have a perfectly flat bottom with integrated pad screw receivers. Traditional key cups are not completely flat on the bottom, so the pad retaining rings (what holds a pad in a cup) put unevenly distributed pressure on the pad, causing it to warp. Flat-bottom key cups solve this problem and more:

• Increased precision to allow pad cup to seal properly with tonehole
• Superior pad fit: In the shimming process (ensuring that the pad seals well with the tonehole), the pad can accurately respond to the shims. Without a flat bottom, response to shims is compromised because of the distortion of the key cup.
• Pads hold their adjustments better and longer.