(Available in D, G, and F major, and a set of ♭B, C, and A major. The triangular prism is fixed when lightly rotated.) This allows beginners and those new to the erhu to easily play with "correct intonation." Advice on Choosing the Length of the Intonation Display Device: Generally, the effective string length of the erhu (the length from the bridge to the qianjin) is set to 39 cm. When choosing an intonation display device, select one of the appropriate lengths from 39 cm, 41 cm, or 37 cm, based on the effective string length of 39 cm, and according to your physique and playing style. For example, if a physically large male finds that the finger spacing is too tight and the fingering is not smooth when playing the third position with an effective string length of 39 cm, they should extend the effective string length to 41 cm and select an intonation display device of the same length. Conversely, if a relatively small female finds that the little finger of the D major first position cannot reach the correct intonation position without shifting the tiger's mouth downwards with an effective string length of 39 cm, it is better to shorten the effective string length to 37 cm and choose an intonation display device of the same length. Utility Model Registration No. 3180571 Product Name: Erhu Intonation Display Device Contents: 2 intonation display rods, 4 attachments, a dedicated case, and an instruction manual