Sdg bel air steel saddlethe bel air saddles are the modern classics providing ultimate comfort support and control the original uses a resilient polypropylene base that allows extra flex on the edges through each pedal stroke and incorporates a base bridge for stiffness and ideal power transfer the 20 possess the same overall technology with a nylon base and the super light sl i beam use a nylon glass fiber in a solid beam design with a honeycomb structured core for the lightest strength