Other attachments can also be fitted, which are even available in half sizes. I recommend SednaEarfit XELASTEC, which are much more comfortable than Sony's originals, which in turn either don't fit properly at all and thus also leak during ANC or then painfully hurt after an hour. The Xelastec also adapt smoothly to the ear canal. Only when you're out in the pouring rain and water gets into your ears do they tend to slip out of your ears as the ear canal gets wetter. However, you notice this quickly and can push them back in. So far, none of the plugs have fallen out and none have been lost. I can now say that the wearing comfort is unrivalled. Apart from that, cleaning is much easier because you don't have foam tips that get soaked with water. I would not make the purchase dependent on the included ear tips, especially since they are replaceable and the WF-1000XM4 still offer an unrivalled overall package and are still Sony's reference model among the ear plugs - until (perhaps) the XM5 come along at some point.

I also seem to have very narrow ear canals - even with the smallest attachment, it is very narrow and difficult to get them in (and therefore uncomfortable).
The Linkbud S are supposed to fit better in small ear canals, as I have read.