Technically, that would be the 11-speed road Shimano Hyperglide.
Though I would buy an "8-910-speed" MTB freehub (if it were me).
There are some caveats, and I'll try to explain, and the buying decision is yours (best I can do is provide all the info, as clearly as possible):
1. The total cassette width vs freehub width
Cassette width in terms of the width of the total stack of all the sprockets and spacers for the 11-speed MTB, and road cassettes is practically the same (see this section in the
cassette compatibility article for more details).
However,
road cassettes have smaller largest few sprockets, so the freehub body needs to be wide enough to accommodate for the entire cassette width.
MTB cassettes, on the other hand, have larger largest few sprockets, so they can "overhang" the hub's right flange and spokes. This allows for a narrower freehub body.
View attachment 150
How freehub widths differ and how they affect the wheel's strength:
Note:
10-speed cassettes are narrower than the 8 or 9 speed cassettes in terms of their total stack width (sprockets + all the spacers). Shimano used to make special 10-speed-only freehubs that were too narrow for the 8 or 9 speed cassettes. Then, they switched to building the same freehub width for 8, 9, 10, and 11-speed-MTB cassettes (11-speed-road cassettes need a wider body). And it is understood that you would use a 1mm spacer (often came with the cassette) when mounting a 10-speed cassette. A few years later, Shimano started building 10-speed cassettes with a wider spider holding the largest few sprockets, effectivelly making the cassettes come with a built in 1mm spacer.
2. Cassette mounting standards
Regardless of the number of speeds as in total cassette's sprocket and spacer stack width (and the needed min. freehub width), there are different
types of cassette mounts (that require matching cassettes), with Shimano being what most smaller manufacturers comply with:
- Shimano Uniglide (now obsolete) - 6 to 8 speeds.
- Shimano Hyperglide (probably by far the most widely used now and over the past few decades) - 7 to 11 speeds.
- Shimano Hyperglide+ (the cassette mounting interface is called "MicroSpline") - 11 and 12 speeds, the latest & greatest by Shimano.
- SRAM XD - 10 to 12 speeds.
- SRAM XDR (for road bikes) - 11 and 12 speeds (not 100% sure about 10).
- Campagnolo Exa Drive old - 8 and old 9-speed cassettes.
- Campagnolo Exa Drive new - 8 speed (not 100% sure about 9-speed).
- Campagnolo Ultra Drive - 9 to 12 speeds.
3. Making sense of it all - hopefully
Generally, narrower hyperglide cassettes will easily fit wider freehubs, you just add spacers. However, note that wider freehubs compromise the wheel's strength to a degree (I consider the 11-speed road freehubs to be a nonsense in those terms).
XD cassettes will fit XDR freehubs with spacers, but vice-versa is not possible, of course, as the road cassettes are "wider" (can't overhang the hub's right flange and spoke ends).
Of course, should you desire to ride Shimano's latest&greatest Hyperglide+ systems (the latest & greatest Shimano MTB 1x and 2x systems, like the
XTR M9100), you'll need a Hyperglide+ (MicroSpline) freehub (unless they've made a Hyperglide+ cassette with a Hyperglide mount).
Again, the non+ Hyperglide (the "old," "standard" one) is most easily sourced and most widely used. The 11-speed road one will give you the absolutetly largest choice of 11-speed Hyperglide cassettes to mount, but at the cost of the slightly weaker wheel (while the MTB Hyperglide freehubs will fit all but the 11-speed road Hyperglide cassettes, unless you manage to source a 7-speed Hyperglide freehub).
Hope I've explained more than I've confused.
Relja