This is a large Perlanco size. This size is for regular Acer use. Large sizes are suitable for elementary school and older years. Diameter 8.3 inches (21 cm) x Height 1.6 inches (4 cm); Diameter = Diameter of the drums striking surface. Height = The height when the surface is placed upward. Size Guide: 8.3 inches (21 cm): Elementary school age to adults; 7.1 inches (18 cm): Elementary school years and kindergarten; 5.5 - 6.3 inches (14 - 16 cm): Kindergarten and nursery. *Recommended for sizes only. It seems to be better to choose a larger size if you are not sure which one is between your previous orders.