Freehub Body Standards: HG, XD, XDR

The Shimano data come from its official freehub and cassette compatibility chart (C-731) and each cassette’s spec sheet; SRAM’s, from its technical article on XD and XDR; and Campagnolo’s, from its compatibility charts and product pages. Everything was checked in October 2026 and cross-checked against ENVE’s freehub guide. The freehub body (or driver) is the splined part of the rear hub the cassette slides onto: if it doesn’t match, the cassette won’t go on.

Which cassette fits each freehub body

Freehub	Brand	Speeds	Smallest cog	Notes
HG M (standard)	Shimano	8, 9, 10 and 11-speed mountain	11 teeth	34.9 mm; the classic freehub
HG L (11-speed road)	Shimano	11- and 12-speed road	11 teeth	36.75 mm; 8-10 speed with a 1.85 mm spacer
HG L2 (12-speed road)	Shimano	12-speed road only	11 teeth	37.65 mm; 12-speed only
Micro Spline	Shimano	12-speed mountain	9 teeth	23 splines; 10-51, 10-45 and 9-45 cassettes
XD	SRAM	11 and 12	10 teeth	Same hub dimensions as an 8-10 speed HG
XDR	SRAM	11- and 12-speed road	10 teeth	1.85 mm longer than XD; takes XD with a spacer
Campagnolo FW	Campagnolo	9 to 12	11 teeth	12-speed cassettes: 11-29, 11-32 and 11-34
N3W	Campagnolo	11, 12 and 13	9 teeth	13-speed direct; 11 and 12 with the AC21-N3W kit

Spacers and combinations according to Shimano

Cassette	On HG M freehub	On HG L freehub	On HG L2 freehub
12-speed road	No	Yes	Yes
11-speed road	Only HG800, HG700 and RS400	Yes	No
11-speed mountain	Yes	With a 1.85 mm spacer	No
8, 9 and 10-speed	Yes	With a 1.85 mm spacer	No
12-speed mountain (Micro Spline)	No	No	No

The CS-7900, 7800, 6700, 6600, 5700 and 5600 10-speed road cassettes also need a 1.0 mm spacer, which comes with them.

How to tell which freehub your wheel has

Count the splines and look at the shape. HG has 9 wide splines; Micro Spline, 23 fine splines; XD and XDR have splines only at the base plus a thread the cassette screws onto.
Measure the length from the cassette seat to the tip: 34.9 mm is an 8-10 speed HG; 36.75 mm, an 11-speed road freehub.
Look at the cassette’s smallest cog. If it has 10 teeth or fewer, it isn’t HG.
Campagnolo FW or N3W. N3W only fits disc brake wheels with a 12 mm thru-axle; Campagnolo has fitted it as standard on its wheels since 2021 and offers a conversion kit for several older ones. Rim brake wheels use the 9-12 speed FW.

You can usually swap the freehub without replacing the wheel if the hub maker sells it as a spare part. Installing the cassette, with tools and torque, is covered in how to change a cassette, and which cassette each groupset uses, in our guides to Shimano road groupsets and SRAM groupsets. Before you buy a new cassette, also make sure your rear derailleur can handle its biggest cog and that your chain has the same number of speeds (the match is in the bike chain width chart). The gear ratio calculator shows what you gain or lose going from an 11 to a 10-tooth cog, and the 1× vs. 2× guide explains when a wide-range cassette pays off. The names of every part in six languages are in the drivetrain glossary.

Frequently asked questions

Will a Shimano 12-speed road cassette fit an 11-speed freehub?

Yes. According to Shimano's compatibility chart, 12-speed road cassettes fit both the 11-speed HG L freehub (36.75 mm) and the 12-speed-only HG L2. What the L2 won't take is an 11-speed or lower cassette.

What is the 1.85 mm cassette spacer for?

It makes up the difference in length between freehubs. You need it to fit an 8-, 9- or 10-speed cassette (or an 11-speed mountain cassette) on an 11-speed road freehub, and to fit a SRAM XD cassette on an XDR freehub.

Can I run a 10-tooth cog on an HG freehub?

No. The HG freehub limits the smallest cog to 11 teeth. For 10 teeth you need XD, XDR, Micro Spline or N3W; for 9 teeth, Micro Spline (XTR and XT 9-45 cassettes) or N3W with Ekar cassettes.

Sources

Updated October 19, 2026 · Report an error on this page