Basic block foam that is kept in bulk at many upholstery shops. Better cushions are engineered to a specific piece and not cut from block. They are not latex (there is no 100 % natural latex, even the purest blends are 92 % latex, most though are closer to 50 %). DuPont Qualax is considered to be the best man-made foam cushion for the upholstery market and they come in different densities.

No idea on the Ultracell spelling....sorry