Fusion-formable glass-based articles including a metal oxide concentration gradient

A glass-based article comprising: a first surface and a second surface opposing the first surface defining a thickness (t) (mm); and a concentration of a metal oxide that is both non-zero and varies over a thickness range from 0-t to 0.3-t; a surface compressive stress of 300 MPa or more; and a CT region having a maximum CT of less than 71.5/√(t).