From Academic Kids
Zils are commonly about 5 cm (2 in) in diameter. Accomplished dancers will often have a second slightly larger set for use in noisy situations. They are commonly made from brass rather than the bronze used for larger cymbals, but many other alloys are also used. Some are plated to give a silvery colour or a brighter surface. Dancers speak of silver tone and gold tone, and may have several sets with different tones for different dances, or of different colours to match different costumes.
Modern dancers use elastic to secure the zils, one to the thumb and one to the middle finger of each hand. A hole or two slots are provided to allow the elastic to be threaded through the zil. There are a variety of ways to cause the zils to ring, resulting in a wide range of sounds that the instruments can produce.
Zils are occasionally used as part of orchestral or other musical performances. In these cases they are usually just called finger cymbals and are used to obtain a ringing sound with "Middle Eastern" associations. Percussionists playing finger cymbals sometimes use a less complicated technique than the traditional one used by dancers. The musician holds one cymbal in each hand by gripping the strap between the thumb and the index finger, and they are played by striking the rims together. This technique is used when the zils are used for occasional flourishes in the music rather than for complex rhythms and sounds.ja:フィンガーシンバル