TOP INSIDE DIAM.
I keep in stock a small number of hand made (in France) etched ball shades($23 ea.)designed to fit both Kosmos #6 (with a $9 adapter) and Kosmos #8 & #10 burners (no adapter required).
Here are photos of the shade and topping a US finger and #1 lamp to show scale. The shade's overall diameter is 4-1/8"; height is 3-3/4", bottom opening 1-9/16";top opening i.d. 1-7/8"..