The special heads are made in Mumbai. The Mumbai head traditions makes heads from skins that are thicker than the typical heads. This makes them a little harder to tune but the durability is much better.
Measure your tabla head size carefully::
If you have the drum without the head: Measure the outside diameter of the drum shell at the top; the bearing edge from outside edge to the opposite outside edge.
If you have the head off the drum: Flip the head up-side-down and measure the inside diameter of the underside of the playing surface.
If you have the head on the drum: Measure the diameter of the head across the playing surface, do not include the braid.