The machine bushing is 12 mm OD, 8 mm ID, and 16 mm long. The key is 3 mm x 2.3 mm x 16 mm long. The key is 2.3 mm thick because the keyway in the bushing is shallow.
See Used On tab for reference to machines using this part and the corresponding drawing number.
In your instruction manual, this part appears on the parts list as: