The special case of the grand piano, called the rim, reveals the design legacy of Steinway & Sons behind the Boston. The rim contributes to the stability of the piano, offering support for the soundboard. The outer rim consists of several layers of mahogany, and the inner rim of the Boston grand is made of hard rock maple. This high-quality hardwood is pressed with horizontally oriented grains, providing more stability, and exceptional power and richness of sound.