Included in item 7 of the exploded view.
With the exception of the axles, the spare parts for the Shimano XTR HB-MT901 and HB-MT901-B, Boost, front wheel hubs are identical. With Boost or non-Boost axles, hubs cannot be converted to the other mounting standard, as the hub bodies are of different widths.
Herstellerinformation: SHIMANO INC., 3-77 Oimatsu-cho, Sakai-ku, Sakai-shi, Osaka 590-8577, Japan, www.shimano.com | EU contact: Shimano Europe BV, High Tech Campus 92, 5656 AG Eindhoven, The Netherlands, www.shimano.com