This ring is made in sterling silver, .925. On the circular face we use a medium star. You could use an actual nickel, to reference the diameter of the star. The ring tapers down to 4mm. We keep the inside of the ring smooth and it's thickness around 3 to 4mm, so that it is comfortable when working with your hands. This is a newer style for us and really becoming more popular for both men and women. This particular style, and has a contemporary feel with its smooth, elegant & modern simplicity.