The SRAM RED AXS ceramic pulley kit replaces the upper and lower pulleys with ceramic-bearing versions built to reduce rolling resistance through the derailleur. The lower pulley runs a metal spider construction specifically to hold up under the chain tension it manages, while titanium pulley screws keep the added durability from adding meaningful weight. Grease is included for installation, and the kit is built specifically for the RED AXS E1 derailleur.