The panel door system is intended for the most demanding users. The doors can be used in single-family or multi-family houses. The design of panel doors is based on the three-chamber AC-77HI system, in which an innovative thermal break is utilised in new doors. It eliminates the negative impact of thermal stresses caused by the temperature difference on the external and internal surfaces of the door. The door is designed in such a way that it is possible to make a leaf flush with the frame from the outside (the leaf profile is invisible from the outside). Door filling comes in the form of one-side overlay panels available on the market. The option to use concealed hinges improves the aesthetics of the door finish.