Round chainrings specifically compatible with Shimano cranks Dura-Ace 9100, Ultegra 8000 & 105 R7000 but can be retrofit to all 9000 and 6800 series cranksRamps on big rings are specially configured for combinations: 50/34, 52/36, 52/38, 53/39TRugged CNC machined 7075 aluminum constructionUse original bolt when changing inner ring only, long bolts when changing outerSuper stiff design due to thicker, 5mm construction110mm 4-bolt39T7075ALOil Slick10/11/12spStandard