Speaking of cables and such, I've seen some pretty nice aftermarket stuff on BA5s here.
Check out this photo from Post 1,888:
I'm using mine stock, but I want to try it with the NiceHCK C-16-3. (Pictured above).
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With regard to QC, I am aware of the issues some people have reported with the BA5. I use my BA5 pretty heavily now, it's one of my go-to IEMs, and I have to update my sig to reflect that. I haven't noticed any issues with it, but there might be moisture buildup, I can't remember. I am actually very pleased with mine and was going to post some comments, but I just haven't gotten around to it yet.
I got one of the good ones. The shell is really, really nice, and feels much more premium than the price implies.