The correct mineral glasses that will fit your 1970’s Heuer Montreal with Cal. 12. You will receive the glass, complete with the gasket needed to fit it on the case. The measurements are approximately Ø37.00mm by 2mm thick and you can see more specific details about these measurements on the main image.
Please do remember that I do not accept returns for parts and do not hesitate to contact me for any questions you might have.