Produced using the most advanced computer design and manufacturing technology, Yamaha Standard Series mouthpieces feature unmatched precision, smooth attack, secure control and easy playability. The 58 has a medium cup and rim for easily playability through the low and middle registers and offers a crisp attack with outstanding flexibility. Similar to a Bach 2G Inner Diameter = 26.84mm. Contour = standard . Thickness= standard. Cut Depth = standard. Throat = 7.25mm. Backbone = semi-wide.