Aye, but the question that arises (in my mind, at least) is: Why? Why choose a higher-price 9-28T Capreo cogset with 311% range requiring a proprietary hub carrier with the increased inefficiency and accelerated wear of a 9T cog, when one can choose a less expensive, regular 11-36T cogset with 327% range, no funky or proprietary parts and improved efficiency and reduced wear of a 11T cog? 🤔

For example, this Shimano CS-HG50-10, 11-36T part sells for less than $30.



Similarly, a Shimano CS-HG400-9, 11-36T sells for under $20.

Finally, something to keep in mind is that folders, particularly the 16" species, tend to have shorter chain stays. The chain stays on my FnHon Gust 16", for example, are a mere only 33cm. Those on the 102cm wheelbase FnHon Storm 20", only 40cm. This means that the chain angle will always be more oblique than on regular sized bikes, which will translate into greater inefficiency and wear on the innermost and outermost cogs. This is less of a problem on the biggest cog where friction and wear is spread over more cog teeth and chain links, but it will really bite you hard on the small cog. For this reason, one will want to avoid a 9T cog on a short-chainstay bike.
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In 2023, Capreo is an obsolete anachronism, imo.