Shimano brand pulleys for mounting on the Shimano Deore/SLX 12- speed derailleur. The derailleur pulleys ensure that the chain is tensioned and guided during shifting. The lower pulley, also known as the "string," is responsible for tensioning the chain, while the upper pulley, referred to as the "pulley," is responsible for the movement of the chain. To ensure good precision and smooth operation, the derailleur pulleys must always be in good condition. They are compatible with the rear derailleurs of the SLX M7100 and Deore M6100 series. Road Compatible derailleur: RD-M7100-SGS, RD-M7120- GS, RD-M6100-SGS Compatible series: SLX M7100, Deore M6100 Number of speeds: 12 Packaging: 2 pieces (high/low) Mounting: Rear derailleur.