Product Description Specification: Product name: Universal finger amplifier for musical instruments Inner rod material: technical fiber inner rod, imported soft rubber casing Ring material: ABS plastic, high-quality thick copper nut Colour: Black Weight: about 40 grams/set (including packaging) Total length: 20cm/7.87inch Inner diameter of index finger: 2.3cm/0.91inch Index finger circumference: 7.22cm/2.84inch Inner diameter of middle finger: 2.3cm/0.91inch Middle finger circumference: 7.22cm/2.84inch Ring finger inner diameter: 2.3cm/0.91inch Ring finger circumference: 7.22cm/2.84inch Little finger inner diameter: 2.1cm/0.83inch Little finger circumference: 6.59cm/2.59inch The package contains: 1PC universal finger expander for musical instruments, 1PC screwdriver, 1PC spare rod Scope of application: guitar, piano, guzheng, violin, erhu and other musical instruments, beginners can't open their fingers. Correct wearing method: Take the left hand as an example. When wearing, the black connecting rod is on the back of the hand, and the screw cap points toward the base of the finger. Incorrect wearing method will affect the effect of physical examination, please develop more training methods by yourself. The finger expander is used without the piano, and cannot be worn when playing the piano.