I just so happen to have these I picked them up like a month ago and i burned them in pretty well and use to use them alot
ill give you my thoughts enjoy
( i did remove the filter which i recommend as it makes them less muddy)
Build
Out of the box they feel cheap but solid. They definitely arn't going to turn heads but they dont look bad either. They look exactly like the KEB/24's with a different color scheme. The cord is definitely not its strong suit the card feels flimsy and lack of any slider to take care of the slack that coupled with the j cord makes these thinks more or a hassle to use if you ask me. The HJE300's had a much beefier cord that felt solid and was of a symmetrical design. They did both however have that small jack that will fit in the iphone which is a plus
They also have a volume control which i like even though if felt slapped on but it works really good i don't know if it add more resistance and it doesn't seem to give any boosts in SQ but as a volume controller it works well and this might be handy if your not into fiddling with you players volume and it is very small and does not weigh down the cord like i thought it would
Sound
This is were they loose points in my book they have basically a very congested/narrow sound stage and have very exaggerated bass it reminds me the Sony's but its has WAY MORE control and depth to it and alot of punch. However this is at a cost the bass mixes alot with the mids and makes the midds muddy to. Vocals seem okay but they feel very veiled to my ears and the highs roll off but they sound sweet and these do articulate better than the sonys. The HJE300's squarely beat it in every regard sonically but they are a better fair sound wise than the sony buds ( this is after removing the filer which actually made things clear up a bit but not enough)
isolation
these koss buds use a unique tip the have a lager opening than most and the bottom were they connect to the tube of the buds is larger. I tried using these tips on some of my other buds and they are somewhat loose because they are so loose fitting on them (you can't really swap the tips). But these do provide a GOOD deal of isolation id say just a tad under the FX-33 but much better than either the sonys or the HJE300's for that matter. This is because they are also much thicker than your usual tips with helps alot and they are pretty comfy but nothing special to note. Although i though the isolation on these to be pretty good despite the fact that these have a hole in the back which i found impressive.
Final word
They arn't bad and they arn't great they are definitely better than your standard buds and sonys buds and have a good bass punch that i thought was nice and some sweet highs but they are way to rolled of the make them feel present to me. They do isolate alot and have a volume control which i found useful but their j cord and well flimsy cord make me worry about durability but id say isolation and bass wise there pretty good but the HJE300 i use now are sonically superior to these in every respect at the same price. Id guess these are those looking for volume control and a step up from the sonys but the FX-33s and the RP-HJE300s i feel is a better deal. But they arn't to bad you can do better however.
And thats my 2 cents