Typical only here (and in the neighborhood). It's about 10 cm (4 inches) in diameter.

The reason for this is coffee. It is mostly cooked in a džezva, or a small metal cup, of 0,5 or 1 liter. Boiling half a liter of water, or less, in any larger pot would make no sense, and would create problems when pouring into cups. Heating such a small vessel on a larger plate would waste energy. Which is why you can recognize a stove made for this market simply by looking for this small plate.

The stoves like this are becoming a rarity - first, coffee is generally not made in a džezva anymore, there are microwaves and then the cups have grown too, so such a small plate has become too small.