Ethafoam - big 21x20x2" pieces, hard stuff. Basically Plastazote style polyethylene foam.
Colleague just sent me two such pieces, it's too hard for my use. Very light, but I suspect people carve it or use it for inside glass etc.
Q: Anyone interested in the 2 pieces - I can put them on Ebay?
Expensive stuff, just can't use it myself (was meant for a case and I suspect he mixed up lb-in & lb-cm re load bearing). It's from a USA plastics firm, grade 1, mint condition (came in a double-crate).
Back to finding an LD24/LD45 source...