A glass-based preform for a mirror of a heads-up display (HUD) system, including a glass-based substrate having a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces; a first chamfer at an edge of the first major surface, the first chamfer having a first end at an intersection of the first chamfer and the first major surface and having a second end at an intersection of the first chamfer and the minor surface; and a second chamfer at an edge of the second major surface, the second chamfer having a first end at an intersection of the second chamfer and the second major surface and having a second end at an intersection of the second chamfer and the minor surface. The first chamfer has a different size or shape from the second chamfer.