These chainrings are for Shimano GRX cranks. They feature our patented Drop-Stop(R) design for the best wear life, chain retention, and mud clearance. Drop-Stop ST is specifically for the Shimano 12-speed Hyperglide chain, which is used by GRX 12-speed. Drop Stop-B works with all other 9, 10, 11, and 12-spd chains, including SRAM Flattop.