Selle Italia SLR Boost TM Superflow Saddle - Manganese Black S3. The SLR Boost TM Superflow saddle marries modern technology and saddle ergonomics to the popular SLR design. It shares the same design and molding as other SLR Boost saddles but at a fraction of the price thanks to the utilization of manganese and chromoly TM rails and a Soft-Tek polyurethane cover.