The QKZ x HBB look and feel like a premium product, its build quality is definitely on the higher end. If anything, the design is a tad edgy. I would have preferred a simpler and discreet-looking IEM. While comfortable to wear, they are not the most snuggly fit. This is in part due to the angle/length of the nozzle, and also due to the very light cable. For $20 the packaging is nothing to complain about. The cable is detachable, and several sizes of eartips are included.
Sound quality is great for the price. I am not much of a bass head and the fact that I have almost always used balanced-armature IEMs may be a factor but I have to say that the lower frequencies hit deeply. They reveal a punchy, full and textured sound that I have never been accustomed to previously, at least with IEMs. In contrast, mids are much subtler, which I understand as a deliberate design choice to take full advantage of the dynamic driver’s strength. The higher frequency ranges are considerably less forward than the bass. I am used to flatter sound signatures and was initially disturbed by the muffled vocals. It took several days to make them feel natural to my ears. Still, after some personal burn-in, I found that although not too detailed, and definitely not as well textured as the bass, the mids and trebles remain decently clean and precise, with good instrument separation and imaging capability.
A good comparison point would be the 7Hz Salnotes Zero, which have similar price and release date. Thanks to its more homogeneous and balanced tuning, this IEM set is much more natural-sounding, but I think that ultimately, the more thunderous and exciting QKZ x HBB are a better bang for the buck. It is not as versatile but focuses better on what it does well. I would definitely recommend them for bass/instrumental/drum-heavy music.