The lockring is available in two versions: with the tool slot on the outside and on the inside. To fit the lockrings with the external thread, you will need the classic Hollowtech II bottom bracket (44 mm outer diameter, 16-tooth spline); for the lockrings with the internal thread, you will need the Shimano or SRAM cassette tool.
The thread on the Centerlock lock rings is standardised and fits all hubs from all manufacturers, except for the older Shimano Saint and Zee hubs. These had an oversized thread, meaning that even standard Centerlock brake discs would not fit.
The Shimano XTR lockring for the HB-M988 Centerlock hub with external tool holder, 44 mm