The lugged cell cups are designed to fit into the Ceracell aluminium mounting bar. The polypropelyne cell cups can be boiled to clean up and sterilise, so you can reuse them over and over again. The downside is that you will get about 50% acceptance by the bees of polyprop cell cups. The Buzzco styrene cell cups get about a 90% acceptance, though they can't be boiled. The melting point for styrene is about 70 degrees C.