The diameter of the dial is approximately 20cm. The material is plastic. It can also be used as a table clock as shown in the photo. It has been in my house for over 35 years. It was used until recently, so it works normally, but the accuracy of the time cannot be guaranteed. Please purchase with the understanding that this is the case. *I've been running it with a battery for about two weeks, and the time hasn't drifted much.