O clock Yellow - Band Only The OClock watch is a silicon watch made by the Italian company Fullspot. What makes it unique is that you can pop out the face and change the band! The OCLOCK watch range comes in 3 sizes (Small; Medium & Large) and should fit most people. Its made of a soft silicon fabrication that easily stretches over you hand and holds its shape very well. The way it fits you is of a personal preference. Some like it tight and some like it loose. The measurements we provide is the CIRCUMFERENCE of the internal portion of the watch. The best way to measure your wrist would be to wrap a string of some sort around it and mark it. Then measure the length of that string up until the point where you marked it off. Keep in mind the silicon stretches. *We obviously cannot guarantee this however! We suggest a wrist measurement.