Cheap Shimano OT-SP41+OT-RS900 OPTISLICK Shift Cable Set for R7000

The Shimano OPTISLICK cables feature a minimal and uniform electrically coated layer that improves cable routing efficiency and provides excellent corrosion resistance. The rear derailleur RD-R7000 must be assembled on the bicycle with a special outer casing, OT-RS900. Purpose of OT-RS900
The radius (r) of the curved cable that is routed from the bicycle frame to the RD-R9100 become smaller compared to the radius generated with other rear derailleurs, as indicated in the images below. The commonly used outer casing, OT-SP41, is too stiff for such small radius that it could cause technical problems on the adjutment barrel and disturb quick and smooth engagement and disengagement of the rear wheel from the frame. By using the OT-RS900, such problems can be avoided as the stiffness is reduced on OT-RS900.

OT-RS900 should be used only on the rear derailleur side. It should not be used on the shift/brake lever side.