the invention relates to a window unit comprising a window pane and a frame . the frame consists of two parts , a basic frame and an additional frame . the basic frame has a bearing surface which contacts the window pane to which the frame is permanently fixed by means of an adhesive layer deposited on the bearing surface . the basic frame further comprises a connecting surface for the additional frame . said additional frame in turn also has a connecting surface of the basic frame . the two frame parts are removably or permanently joined together via their connecting surfaces .