Freehub compatibility: HG, XDR, XD, Micro Spline and N3W
Match your cassette to HG, XDR, XD, Micro Spline or N3W, check spacer exceptions, and prepare the details needed for a custom wheelset quote.
Choose the freehub from the cassette's exact model number before choosing a hub upgrade. "Shimano 12-speed" or "SRAM gravel" leaves too much room for a mismatch. Two bikes with the same number of gears can need different cassette interfaces, and the right interface still needs the correct hub body and end cap.
The schematic diagram accompanying this guide is an orientation aid. Use the manufacturer's compatibility information and the proposed hub's part number to confirm the build.
Find the cassette model first
Look for a code on the cassette, its lockring, packaging, or purchase record. Record the brand, model, number of sprockets, and smallest and largest sprocket. A clear photograph helps when the code is hard to read. Record a planned drivetrain upgrade separately from the equipment fitted today.
Ask the wheel builder to check that specific cassette against the proposed freehub. A groupset name is useful context, but the cassette is the component that must mount on the body.
Which interface does the cassette need?
| Freehub interface | Starting point for checking fit |
|---|---|
| HG spline L, often called road HG | Shimano road 11- and 12-speed; check model-specific spacer exceptions. Shimano compatibility chart |
| HG spline L2 | Shimano road 12-speed dedicated; excludes road 11-speed cassettes. Shimano compatibility chart |
| Micro Spline | Shimano 12-speed MTB cassettes, including those used by GRX 1x12. Shimano freehub guide |
| XD | SRAM XD cassettes. SRAM cassette manual |
| XDR | SRAM XDR cassettes; XD cassettes require a 1.85 mm spacer. SRAM cassette manual |
| N3W | Campagnolo cassettes starting with 9 or 10 teeth mount directly; 11- or 12-tooth starts need an adapter. Campagnolo technical FAQ |
Use this table to narrow the question, then check the exact cassette. It does not cover every cassette generation or aftermarket design.
HG is a family, not one body length
Shimano distinguishes HG spline L from the shorter HG spline M and the road 12-speed-only L2 interface. Its chart lists CS-HG800, CS-HG700, and CS-RS400 road 11-speed cassettes as compatible with HG spline M, or HG spline L with a 1.85 mm spacer. Those exceptions are why a general "11-speed HG" description needs clarification. Shimano compatibility chart
For a gravel bike, identify the cassette before relying on the GRX name. Shimano's GRX 1x12 uses MTB cassettes and Micro Spline, while its HG guide also covers road and gravel 11- and 12-speed cassette applications. Shimano freehub guide
In a quote request, write the cassette code alongside "HG" and ask which HG body the builder proposes. If a spacer is required, ask for its thickness and whether the build includes it.
XD and XDR have a one-way compatibility rule
SRAM specifies that an XD cassette can fit an XDR body with a 1.85 mm spacer behind the cassette. An XDR cassette requires an XDR body. A spacer does not turn an XD body into XDR. SRAM cassette manual
Before moving an existing cassette to new wheels, confirm both the cassette type and the spacer arrangement. When ordering a replacement freehub, include the hub's exact model and freehub system; "XDR" describes the cassette interface, not a universal replacement part.
N3W needs the correct adapter and lockring
Campagnolo specifies AC21-N3W for cassettes starting with 11 or 12 teeth. The kit includes an extension ring and a longer Z11 lockring for an 11-tooth start. A 12-tooth start requires the corresponding specific lockring. Campagnolo warns that standard cassette lockrings do not safely reach the thread with the adapter installed. Campagnolo technical FAQ
Ask the builder to identify the complete adapter and lockring arrangement in writing. A quote that says only "Campagnolo compatible" leaves an avoidable question unanswered.
Check the complete wheel before requesting a quote
Prepare these details together:
- Cassette model and any planned replacement.
- Bike model, year, front and rear axle dimensions.
- Rotor attachment and the rotors you intend to reuse.
- Proposed hub model, freehub body, and required spacers or adapters.
- Intended use and any compatibility detail you cannot yet verify.
Use the wheelset finder to shortlist a starting model, then put candidates in the wheelset comparison. Check the product's actual option list. For example, the R50 Aero lists HG, XDR, and N3W; the M25 XC lists HG, XD, and Micro Spline. A drivetrain requirement outside the listed choices needs a written compatibility review before proceeding.
Browse the gravel wheelsets with particular care if you need Micro Spline: the current gravel catalog lists HG, XDR, and N3W. Send the cassette code with your quote request. The final hub variant, compatibility, availability, and price require confirmation in the written quote.
Related posts
Choose rim depth, tire fit, freehub, hubs and spokes with source-backed buying guides. Compare catalog builds before requesting a written quote.
