Orff-Schulwerk style tenor-alto xylophone. Sonor calls this middle instrument the "tenor-alto" since it features an extended range of two octaves (most Orff instruments are 1.75 octaves). An instrument with fiberglass bars is an especially good choice for humid climates, since the fiberglass bars are not affected by temperature or humidity changes. The resonator box is made entirely of wood to ensure true resonance and clarity of sound, and features holes to store your mallets when not in use and a bar storage holder to hold F# and Bb bars when not in use. Dimensions of the resonator box are approximately 33.25" long x 8.88" high x 7.75" wide at the widest point, and 4.63" wide at the narrowest point. With the bars on, the widest point is approximately 10.75" (the length of the low C bar).