a common circumferential rim 18 by a circumferential weld in the embodiment shown here so called heat paraffins i e phase change materials u201c pcm u201d are contained in an evenly distributed manner in the two component silicone rubber mass the melting range of the heat paraffin selected here will be in the range of from approximately 33 u00b0 c to approximately 37 u00b0 c these heat paraffins have a specific melting heat or melting enthalpy which is very high for organic substances at 108 kj kg to 250 kj kg accordingly if the skin surface temperature increases to this level the pcm material is melted a correspondingly large amount of melting energy is required for this which is led away from the skin surface as heat and causes a pleasant cooling effect here if the skin surface temperature falls below the melting temperature of the heat paraffin at a later time the material gives off the energy i e the latent heat during solidification of the material the temperature fluctuations are thus restricted in a small range and effect a substantially enhanced comfort in wear a breast prosthesis formed as a two layer prosthesis is illustrated in fig2 the outer layer or body 20 is comprised of a conventional addition vulcanized two component silicone rubber that is of a standard silicone it can alternatively be.