These handcut circles are made from Tiffany glass that is 3mm thick. There are 2 hard to find sizes 25mm and 40mm diameter. Other sizes can be found on our popular circle sheets (look under specialty sheets). The circles are not perfectly round or smooth as they are handmade so a grinding stone might come in handy to smooth any small roughness. These circles are frost and UVA resistant and can be used in Tiffany and stained glass projects as well as mosaic. Cut in half or quarters they make great petals, wings, scales or a variety of usefull hard to cut shapes.