SHIMANO J-KIT: How to install brake by @world.andrews - YouTube
Disc brake set rear Shimano XT BL/BR-M8100 J-kit (code:IM8100JRRXRA170) ➤ Buy by price 132.90€ - Biketek
Shimano Dura-Ace ST-R9180 Di2 TT Shifter/Hydraulic Brake Lever Set with BR-R9170 Flat-Mount Brake Caliper and J-Kit Fittings, Rear/Right - In The Know Cycling
Shimano GRX with J-kit | Mountain Bike Reviews Forum