This is a filament rear entry bracket that incorporates the CR-10S filament sensor. This bracket physically and tightly is secured to the Z bracket wheel screws. This design uses the CR-10S filament sensor and sensor cap (but not the sensor base). There are features meant to zip-tie the X motor and sensor wires along with the extruder motor wires, and the hotend and filament sensor wires can route through the bracket interior.
4mm OD tubing snaps nicely into place within the design to gradually guide filament from the sensor 90deg into the extruder motor.