The Shimano OT-RS900 Rear Derailleur Loop is a crucial 170mm section of RS800 housing. Specifically designed for use with Shimano's R9100, R8000, RX800, R7000 series Shadow style rear derailleurs, this loop is indispensable for proper functioning. Essential for 2nd generation 11-speed road rear derailleurs, its design accommodates the entry angle into the derailleur adjuster, requiring greater flexibility than the OT-SP41 housing used elsewhere in the drivetrain. This ensures reduced drag and optimal functionality. Compatible with Polymer coated and Optislik cables, it's the perfect fit for R9100, R8000, RX800, R7000 drivetrains.