It's a hard plastic internal, covered by a rubber sleeve. Much like the Otterbox Defender series cases. Adds an about a 1/4" ridge about the screen, so you don't have to worry if you place the tablet face down. Total thickness is about 1/2". As far as pocketability, I couldn't tell you, my pockets aren't big enough, even before the case. I can tell you, I have it in and out of my work bag, and I have no issues with it. The IR port is still accessible, the SD card slot is not, you have to remove the case if you switch out the card a lot.
Here are some pictures with a monster can for scale