Does not quite provide the noise isolation that I was hoping for but my needs were perhaps too niche because of the particularly noisy environment I operate in. The eartips package was also opened from the bottom but there were no other signs of prior usage. I don't have any doubt that it is the genuine article based on the performance and build, but just thought I'd mention it anyways.

I ordered the large pair. It is a bit tough to get on and off on my blon bl-03 and moondrop aria but I would consider that a plus personally. Getting a good seal in your ear is a bit of trial and error, especially with the one-liner instructions that come with them. But once you get a good seal, I found that it stays put pretty well. Noise isolation is pretty much on par with stock eartips but the seal and long listening comfort is way better in my case.

Most IEM stock tips do not fit for me. However the Spin Fit Large do the job, and do it incredibly well. They are now my go-to tips when I want to listen to good music (, since I get a perfect seal with them). The only other tips that fit me are the memory foam ones, and those are waay too delicate. The bass extension on these is even better than the memory-foam ones, though the mids are a bit recessed. If you are in for the 'V' shaped, 'exciting', 'fun' sound these are it.

Shoutout to Theaudiostore. One of the best online platforms I have come across in India. Very fast delivery.
Coming to the tips.
Comfortbale than stock tips but less than foam tips.
I bought it for my Blon-BL03s as they have fit issues with stock tips.
Sound doesn't change a lot.(As compared to foam tips as they emphasize bass a lot)
Both highs and lows were perfect.
I seriously recommend guys to try these tips if your BLONs are giving you a hard time.

If you want your iems to have a perfect seal buy these. Bass got punchier and decent improvement to the sound but are a bit pricer for a pair of eartips.
Having great experience with them though.