The SP01 shell system developed by Selle Italia is a wonderfully innovative design. While not the first rear section split shell saddle developed, what makes the SP01 truly new and truly effective is the construction and shape of the shell itself. It is inherently strong but allows independent engineered flex for each side of the saddle without compromising structural integrity. The result is greater comfort for many cyclists, and ideally some increased power down to the pedals, though this may be more individual than saddle fit can be. In this version, you get the Superflow channel and the Carbon-Keramic hollow oval rails of the Kit Carbonio line.

The shape of the SP-01 series varies with length and set-up, but the SP01 Kit Carbonio Superflow has a mild curve top shape, with supportive wings, and when the saddle is leveled at the center section, the tail has a mild lift. The top does support the bone structure, while the Superflow relief channel has been shaped to protect the nerves and soft tissue of the body, while preserving natural blood flow. The saddle is offered in two widths so you can find the proper sitbone support. Having the raised tail profile gives you a source of support when you go low and drive for more power. For some people who prefer a slightly curved shape, the tail also provides more stability when sitting up. You don't truly conform to the shape, but the contour follows a more natural shape for the body. Today's flattest saddles can feel little to much like one is perching on the saddle, and that may be great for some body types or preferences, but not all.

The key to the SP01 is the engineered flex of the shell, and again, this may well be a preference. Many people find it very comfortable, but can't get used to the pedaling flex. Others love it. It's not soft or easily flexed, but feel and perception are part of the decision making process. By utilizing their carbon-nylon polymer composite, Selle Italia ensures they can control the amount of flex, as well as the material's resiliency to constant use. It is tuned for strength and support, allowing the rider weight and positioning to determine the flex. The shell has a folded curve, with the top section following the rider while the lower section is designed for the Carbon-Keramic oval rails to be bonded into. The lower section is thus stiff, and the flex of the shell is essentially a simple squared C-shape spring. As the nose is fixed, and the rails support the central zone at the bottom, Selle Italia calls the action Suspension Link Movement.

The proven hollow oval rails add stiffness and strength at a light weight, and also serve to damp vibration that travels from the road up the seatpost. Perhaps this effect is mitgated by the SP01 design, but it is the high frequency vibration or "noise" that can fatigue the less active, supportive muscles over long hours on the bike. The cover is the Fibra-Tek synthetic leather, with noted durability, weather resistance and micro-perforations, which not only allow the saddle to breathe a little, but also had subtle friction so you don't slide too easily on the surface. A dense foam padding is applied in between the shell and cover, at a moderate thickness, with some extra around the Superflow channel edges, but less on the nose. Apparently though this a traditional length model, the designers felt the SP01 design favored less overall movement as the flex action can be beneficial to power and comfort. If you slide forward for short periods you will be fine, but you won't want to live "on the rivet". Selle Italia considers both width versions to favor riders with less natural hip angle- so perhaps more bent from the waist then from rotation of the hip. If you feel the numerous saddles you have tried, and the discussion of the width, channel, flex, and shape makes sense to you, it may just be time to ride the Selle Italia SP01 Kit Carbonio Superflow Saddle.