The Arpa is a type of harp, a folk instrument from Latin America. This product is a stainless steel "jabe," a ring-shaped tool used to produce half-tones when playing the Arpa. As it is handmade, please allow for slight dimensional errors and minor scratches. The jabe itself is approximately 3mm thick, with an inner ring diameter of 16mm, equivalent to a US size 10 ring, but it is designed to be adjustable to some extent. If you tell me your ring size, I can adjust it to your desired size before shipping.