absoluteBLACK Premium Shimano 110/4 bcd compatible oval chainrings are designed for new type of Shimano cranks Dura-Ace 9100 & Ultegra 8000 only. These are finest oval chainrings on the market in terms of shifting, smoothness of pedaling and manufacturing quality. (They can be also retrofitted to 9000 and 6800 cranks).Size (Mass +/-1g):34T (31g), 36T (37g), 38T (41g), 39T (42g), 50T (120g), 52T (137g), 53T(139g) Compatibility:Shimano Dura-Ace 9100, R9150 Di2 and Ultegra 8000, R8050 Di2. They can also retrofit 9000 and 6800 cranks but use bolt covers for best appearance.Bolts:For Outer chainring please order "Long bolts" from us OR Bolt CoversChanging Inner chainring to oval only? use original boltsMaterial & Finis:CNC machined 7075 Txxx Aluminum. Long-lasting construction. Type II anodizingOvality:Optimized to each size separately. 34T- 6.5% ; 36T, 38T, 39T- 11.4%, 50/52/53T - 10-11.2% ; Timing of 108 -110.5° after TDC (top dead center) - Ideal for road climbing. Patent PendingIMPORTAN