I just received the new Moondrop "Spring" tips a few days ago and am testing them with the Sony IER-M9.
These tips are very interesting. They have a slightly narrower stem, which sits very securely on the 4.8mm M9 nozzle which has a rim of 5.4mm. I did not manage to fit them onto the Moondrop Variations.
From the narrow stem, the tip opens to a wide bore with a quite narrow edge and a very soft, slightly sticky, "umbrella" that is ribbed on the inside. I have rather small and somewhat oval ear canals and the small Spring tip gives me a deeper fit than I have managed with any other tip so far. The soft umbrella seals well and sits comfortably, but allows for good control of vacuum pressure. The M size tips also fit well but the M9's shell sits a little further out with this tip, which changes the sound characteristics a little.
As always I need more time to form a final opinion but I think these are very good, and different to any tip I have tried so far (and I have lots of tips...)
First impression is a clean, open and energetic sound with wide and deep stage with good separation and positioning. Bass is really good too, punchy, clear and extended. My previous favorite tip for the M9, the JVC Spiral Dot++ sound a bit smoother, with a more compact stage and less clear separation and a more mid centric sound. This might at least be partly due to insertion depth and seal, but I have to say the result with the Spring Tips is great for me and my ears. Highly defined, clear, extended, punchy, and comfortable. Well done!
They get a "highly recommended" from me
Moodrop Spring tips are available from the Moondrop store on Aliexpress
Source: Chord Hugo 2, tested with various music styles, Classic, K-Pop, Sound Tracks, Acoustic, Jazz, Pop a.o.
Photo is showing the 3 sizes, they came in individual packs of 3 pair per size, I just mixed them to have a complete set in the picture