Zills are tiny cymbals worn on the fingertips of the thumb and third finger, and used to accompany rhythmic dancing including Belly Dance

They are struck together on an angle so the edge of the upper zill catches the lower and a sharp chime is emitted.

Zill is the Turkish name for these cymbals.
Other languages call them "Sagat" or "Sunouj" (Arabic)  and  "Zang" (Persian)