Abstract: A chair base includes a central opening configured to receive and support a post essentially vertical in an operating position of the chair base, and at least three, preferably five, arms which project radially from the opening. At least one of the arms has a substantially U-shaped profile or a substantially O-shaped profile along its longitudinal direction starting from an outer arm end, and the at least one of the arms also has a substantially I-shaped profile or a substantially T-shaped profile along the longitudinal direction which differs from the U-shaped profile or O-shaped profile.

Abstract: A composite part includes a load-bearing plastic part with an outer contour. The outer contour has at least one outer contour area which, in the case of a deformation of the plastic part, can be exposed to a tensile load. At least one mat is arranged at least in the outer contour area, and the mat is connected at least in areas to the outer contour area in a force-transmitting manner and is formed to absorb the tensile load occurring due to the deformation and thus to counteract the deformation of the plastic part.