The series include 38 & 40 mm for women & men, We use a special technique to fill in the shiny silver powder in the plastic material, so the user can see through the strap and sees the shining spots in between, this fantasy look surely attracts people's attention, and the narrow strap design provides another slim idea for the users. it is the best choice to own for yourself or as a present for your beloved, while you are working out, hiking, playing sports etc. This product will suit your need.