This is a superb antique champagne glass.
Heavy cut crystal.
Nineteenth Century Saint Louis crystal.
(No mark before 1936).
The famous pattern: TRIANON, created in 1830.
Still for sale in Saint Louis factory shop ( price: 160,00 euros for one glass ).
Hight: 10,5 cm
Diameter: 9,5 cm
Period: XIXth Century
Here is a converter inches / cm to help you with the dimensions: