Compatibility Help

Tips to ensure you buy the right parts for your build.

Getting the right part starts with knowing exactly what parts your bike already has. Here is how to identify the details that matter most for the parts we sell. When in doubt, the Will it fit and Questions sections on each product page spell out the fit, and you can always email support@hammerandhowl.com.

Identify your freehub

Your cassette slides onto a splined body on the rear wheel called the freehub. The ones you will meet most often:

  • SRAM XD and XDR. A smooth threaded driver with no tall splines showing; the cassette threads on with a built-in lockring. XDR is about 1.85mm longer than XD, and a 1.8mm spacer adapts an XD cassette to an XDR freehub.
  • Shimano HyperGlide (HG). Tall straight splines with one wide spline that indexes the cassette; secured by a separate lockring.
  • Shimano Micro Spline (MS). A finer splined pattern used for 12-speed Shimano.

To identify yours, the easiest route is to find the specification for your bike or wheels. If that is not possible and you need to check physically, take the wheel off, remove the cassette, and look at the freehub body with the cassette removed. Each cassette page states the freehub it fits. Because a cassette is usually tightened on very securely, you may need a breaker bar and a chain whip or vise whip to get it off. If all of that sounds like a foreign language, consider visiting your local bike shop for help, or spend some time watching how-to videos so you understand how a cassette fastens to the wheel before you take yours apart.

Read your rear derailleur model

Derailleur cages and pulleys fit by derailleur model, so it helps to know exactly what you have.

  • SRAM prints a model on the derailleur, usually in the form RD-[group]-[type]-[generation], for example RD-RED-1E-E1. The group is the level (RED, Force, Rival, GX, X0, XX), and the generation separates the versions.
  • Shimano marks a model such as RD-M8100 on the body.
  • Ingrid and other machined derailleurs carry the model name on the part.

If you cannot find a marking, note the brand, the speed count, and whether it is a road, gravel (XPLR), or mountain (Eagle) derailleur, then check the compatibility on the cage or pulley page.

Measure a thru-axle

A thru-axle has to match your frame or fork exactly. Three dimensions decide the fit:

  • Diameter of the axle shaft, usually 12mm or 15mm.
  • Thread pitch, how far apart the threads sit, most often 1.0mm, 1.5mm, or 1.75mm.
  • Length, the total length and how far the threads run.

The surest method to learn what you need is to remove your current axle and measure it, or match it to a new axle by these numbers. Each thru-axle page lists the diameter, pitch, total length, and thread length, plus the frames the axle is confirmed to fit.

Carbon-Ti X-Lock EVO thru-axle heads in a row, showing the different head shapes and lengths.

Still not sure?

Every product page has a Will it fit section and a Questions section written for exactly these decisions. If you are still unsure, email support@hammerandhowl.com with your bike or your current part, and we will help you get it right.