Very neat Leon,
The size and thickness vary slightly with the different colors. I still need a few for my set (five I think, plus the few team variations). Most of mine were acquired from one high school principal last summer. He sold a complete set individually, most all of which were this color (thick cardboard):
I'm planning to measure each full color variation later today and add to this thread. The SCD indicates all cards are 3 x 4 or thereabouts, which is close, but not correct for all.