TI 316: 7mm rails are hollow titanium, a balance of strength and light weight \n Manganese: 7mm rails made of a Manganese and CrMo alloy for excellent durability and value \n Fibratek: Selle Italia's latest cover material offering supreme durability and comfort \n For more information on idmatch visit http://www.selleitalia.com/en/idmatchsystem/ \n L3: “Wide” intertrochanteric distance and high pelvic rotation (Flow and SuperFlow saddles) \n S3: “Narrow” intertrochanteric distance and high pelvic rotation (Flow and SuperFlow saddles)