Borosilicate Toughened Glass Build Plate is best for 3D Printing because it is rated at a much higher temperature than normal glass and won't crack from heating cooling cycles of a 3D Printer.
Diameter = *170mm, 180mm, 205mm and 220mm
Thickness = 3mm
*Usually size for Kossel mini
**Mainly material is borosilicate which is a heat-resistant type of glass. The edges are manually ground down so you won't cut yourself.