JWS bifold series is a 4-grade system, 50, 68, 80 and120, for different size application. 68 and 80 bifold already has thermal-break version. 68 bifold is standard bifold system for regular applicaiton up to 3000 high. 80 biold is the heavy duty system for oversized applicaiton up to 3600 high. 120 biold the ultra heavy duty system for mega size applicaiton up to 6000 high. PS68, PS80 and PS120 bifold system, has unique pinch-safe sash design to offer safety to children and new user.