Fits all FSA ABS (asymmetric bolt spacing) cranks like the Gossamer, SL-K, and K-Force, including both 4 & 5 bolt designs (while only utilizing 4 bolts). For Gossamer use original FSA bolts and spacers; for SL-K use original FSA bolt covers and bolts; for K-Force must use Absolute Black bolt covers, purchased separately. Inner and outer oval chainrings are optimized with smooth shifting in mind. Features smooth angled surfaces, (6) up-shifting ramps (outer ring), and (12) down-shifting points (outer ring). Oval rings help the rider to spin smoother and more efficiently. Example: 32t is equivalent to 30t at dead spot and 34t at the power zone. Compatible with 10/11/12sp and Di2. Designed in UK, manufactured in Poland. Third party online retailers must be preapproved by manufacturer