It was briefly discussed a long time ago, when KZ switched from the grey color to the black color. But it’s not a topic that comes up too often.
Believe it or not, there’s actually 3 different Starlines.
The original grey ones are ‘thick’, and are made from a stiffer silicone. It also has a ‘grainy’ surface texture to them that seems to grip my ear canals better and stay in place.
The original black ones are basically like the grey ones. Still the same thickness and grainy texture. The difference (besides the color) is that the silicone is a little softer. Not much, but definitely noticeable.
The ‘new’ Starlines are black as well, but noticeably thinner and made from much softer and more flexible silicone. I think they 1st came on the ZS4 but I don’t remember for sure. I have seen them on other models since the ZS4.
The newest black ones are the most comfortable to me, due to being thinner and more flexible.
Hopefully, we’ll be able to buy the newest ones separately. If and when that happens, you unfortunately wouldn’t be able to tell which is which from seller photos though. You’d have to examine the newer black ones in person (side by side with the original black ones) to make sure.
I am not sure if there’s a sound difference between the 3 versions. In theory there should be. But I’d suspect the difference is small. The external size, overall shape, and inner bore is the same.
The primary difference is comfort. The newest black one is most comfortable to me, but it slides out easier. The old grey one stays in place like kung fu death grip.
