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I run two different eMTBs - a hardtail KTM Macina Action (2014), and a full-sus Scott E-Genius 730 (2017). In rear cassette terms, the bikes were supplied with a Shimano HG-50 and a Shimano HG-81 respectively (since the Scott is the more expensive bike, I assume that the HG-81 is a better cassette, perhaps in materials or expected longevity).

Both cassettes are 11t to 36t, and both are ten-speed; I've not counted the non-outer cogs but I would assume they are the same. Historically I have purchased cassette+chain bundles, and always bought the model to match the factory-supplied unit.

However these models are getting a bit older, and my (large corporate) suppliers for the UK do not stock them, suggesting that perhaps ten-speed is dying as an MTB format. Thankfully, eBay UK has stock of both.

Are these two cassettes interchangeable? I'd like to understand that question in relation to these specific cassettes, but also, how can I answer this question in general? For example, if Shimano offer a range of 10-speed MTB cassettes, and they all begin with "HG", is that enough to know they are compatible? If not, what should I look for (e.g. in terms of the name of the mounting type) so I can select other 10-speed Shimano cassettes, knowing that they will fit?

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Both cassettes are functionally equal. The HG-50 is 100% steel while the HG-81 has an alloy spider for its larger sprockets and extra milling to reduce weight and improve shifting performance.

Generally Shimano cassettes for a given speed range and discipline are interchangeable. What you need to watch out for is the change over to Micro spline in the 12x cassettes which is a new interface but as you noted those don’t have an HG prefix.

If you can’t find Shimano, SRAM and Sunrace also make nice ramped cassettes. I’ve never had an issue mixing and matching in a decade of 10 speed maintenance. The tech is all compatible.

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  • Oh great, so I can buy non-Shimano too? I had no idea that the cassettes were that mixable. :=)
    – halfer
    Jul 9 at 23:17
  • If I were to buy a 10-speed SRAM cassette in the MTB category, would that be enough to know it would work? I assume the HG prefix is Shimano only, and thus SRAM would have their own code system.
    – halfer
    Jul 9 at 23:18
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    Yes, it’ll work fine. The PG-1030, 1050 and 1070 cassettes with an 11-36 range are all suitable for a 10x mtb drive train. Jul 10 at 8:20
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    HG, or "HyperGlide" is a Shimano invention that has been either licensed to others or the patent ran out and others have been free to copy. When one goes to shop for a replacement cassette for a Shimano branded one, as you imply you're going to do, one can say they are searching for an "HG compatible" or simply, "HG" cassette. That's followed by the number of speeds. Thus, despite the various manufacturers and their differing model nomenclature, you are still (correctly) after a 10 speed HG cassette.
    – Jeff
    Jul 15 at 3:40

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