My paint supplier told me there were much cheaper urethane paints available, so I sent a note to PPG. Told them we loved Concept, but it was getting hard to get (in my county) and very expensive. Asked if other urethane paints would be a suitable substitute for Concept? Got a nice reply that stater poly-urethane paints would become brittle with age. Concept is acrylic-urethane (not poly-urethane) and remains slightly flexible throughout its life span.
JJ