Unknown foam

While I understand options like acoustic wool makes a very good sound/vibration insulator, I’d rather not have something that messy in my ‘bot.  I’d be happy to use a material that doesn’t insulate as well, as long as it is clean.

I found this short strip of gray/black foam padding lying around my house among my daughter’s things.  She had no recollection where she acquired it and believed she might have another piece somewhere.  My MakerBot Cupcake CNC came with a large amount of this kind of padding – but it was pink.  I didn’t have any of the pink stuff left over, otherwise I would have used it in place of the cardboard as the insulating material for my DrawBot’s stepper motors.

So – do you know the name of this foam padding?  Do you know where I could pick up a few square inches of it to use as a sound/vibration insulator for my DrawBot’s stepper motors?