Product Features: Take with a tuning fork "standard form" is one of the important link in the process of piano tuning. The importance of it lies in the relationship between the sound of a piano and the position of the pitch. Tone temperament order: 1. Determine standard voice 2. The standard pronunciation of each group derived reference tone key tone 3. In reference tone set as the standard sound of the keys is derived for each remaining key tone 4. pitch reference tone group tone keys, each key test the rest of the pitch of the sound Absolute standard A-440Hz tuning fork, sound sensing performance. Soft Shell Case can better protect it from wearing out. Basic Information: Material: steel Size:4.88*0.79*0.39 inches Weight: 1.17 ounces Package Weight:1.41ounces Note: Individual products may have errors, if the product has a problem please contact us. If you have any questions, please feel free to contact us.