20cm X 20cm. 
 
SECONDS - Please be aware, I was trying a new glass out and therefore this isn't quite upto a standard I would be happy to charge full cost for. The clear glass is ribbed and the copper foil has not adhered to all ridges. This has no effect on the structure of the item but may effect it's longevity therefore I am selling at a reduced cost.
 
Please be aware this product contains lead and is hazardous if consumed please keep out of reach of pets and children.