Which Damping material?

My madisound kit came with their dampening foam sheets for the cabinet sidewalls. The stuff looks like 1" thick yellow furniture foam.

I was expecting some sort of denser black or grey acoustic foam.
What are you guys using for full range speakers. The speaker designer mentioned he used a thin rubberized material on the original design.

I'd rather get something decent if it's reasonable and use the madisound "furniture" foam for something else with less expensive drivers.