These are 21mm and 5.8mm high approx. These are solid. They are hard to find today, these are pretty much a half sphere. The way I use these is to drill a hole in the middle, then these can be used as beadcaps or I solder these onto my project, and I have perfect bumps on it! well they stay just where I put them. You can solder two of these together for a sphere. Anyway you get 4 of these domed discs.
R-25-Flor, Type of Metal- Copper, Brass or Bronze, Grade of Metal- 1st Grade, Gauge of Metal- 20 Gauge, Measurement- 21mm, Tall 5.8 mm, Quantity- 4,