Our 450U, 440U and 425U models are insulated with our proprietary polyurethane blend for maximum insulation and rigidity. The 354S, 350S, and 340S models are insulated with a polystyrene core and come in a variety of gauge options. Both the 325S and 324S models are also insulated with polystyrene and are equipped with our FingerGuard™ pinch-resistant section joints to promote safety and reduce risk of injury.