This was on my Tarmac briefly but it’s not quite right for my derrière. Amazingly light, 158g according to my scale. I’m including the Specialized seat post clamp need for 7 x 9 carbon rails, new (Specialized part number 2812-9050) From Specialized: The extremely lightweight S-Works Power saddle has a stiff, FACT carbon shell and rails, and is a high-performance saddle that's designed to help you perform at your best. Its Body Geometry design, with our lightest level of padding, caters to both men and women, and helps deliver superior performance in all seating positions. Proven through blood flow testing and pressure mapping, the extra wide and elongated Body Geometry channel and proper sit bone support provides all day comfort.