Europa-List: What material is the thin yellow foam?

[Andrew Sarangan <asarangan@gmail.com>]

Does anyone know what that thin (1/8"?) yellowish foam used
extensively on the aircraft? Searching through the archive, there was
a mention of it being PVC foam. Aircraftspruce and Wicks do not seem
to have anything that looks similar,  The only 1/8" foam I could find
was Divinycell PVC foam, which is blue and has a density of 3 lb/ft3.