High-Density Foam perfect for needle felting. Made out of safe, North-American foam.
 
Available in several sizes: 4x3x2", 5.5x4x1.5", 6x6x2", 7x7x1.5", 12x8x1.5
There's also the option of adding Gebecon 36g needle(s) and Single Tulip Tool Holder