Spheroid screens place all points an equal distance from the electron gun.
The tubes are inexpensive, but are difficult to view up close, since the middle of the screen bulges noticeably. These screens are not really flat, but are based on a design that greatly reduces the amount of screen curvature. The cylindrical design shapes the screen as a section of a cylinder. This results in a screen that curves left to right, but does not curve up and down. The advantage of this design is that it tends to have less of a problem with glare, since most light comes from overhead.