A process for filling an electro-optic rearview mirror reflective element assembly includes providing an unfilled mirror cell and providing a filling element having a fluid reservoir, a mirror cell receiving portion, and a channel that provides fluid communication between the fluid reservoir and the mirror element receiving portion. The unfilled mirror cell and the filling element and compressible sealing element are positioned in a vacuum chamber such that the mirror cell receiving portion receives an upper portion of the unfilled mirror cell. Negative pressure is established in the vacuum chamber and electro-optic fluid is provided at the fluid reservoir of the filling element, with the fluid flowing through the channel and passageway and fill port to fill an interpane cavity of the mirror cell with electro-optic fluid. After filling the interpane cavity, the filling element and sealing element are removed and the fill port is plugged.