Why I got them:
I wanted a more convenient monitoring setup at band practice. I have IEMs from shure that I've been using for years, but for just practice it is some what annoying to use IEMs, because putting them on and pulling them out is hassle, also since I wear foam tips, they wear out the more I use them.
Superlux:
I'm very familiar with Superlux products, buy them pretty often and I'm usually pretty happy with the price compared to the product I get. In my experience if you buy two of them same product, they will sound different, because the quality varies a bit. They tend to use really good plastic, and every headphone from them I've broken, just had a cable failure, easy soldering job if you know how. (I don't abuse my gear, so if you do, you mileage may wary)
Audio:
The audio quality isn't as good as I've had with other headphones from superlux, but plenty good enough for monitoring. I wouldn't use these at home for listening to music or while doing mix/master work. The high end sounds dull and the bass lacks something.
As earmuffs/hearing protection:
These do the job, pretty well. Very comparable to my SE315 IEMs. I have limited experience with generic earmuffs, so take this with a grain of salt, but to me they are pretty much the same.
Build, design:
Plastic, but pretty sturdy and flexible, I don't feel like these are going to break easily. The removable cable is a plus on that, though it is the weirder design where a really short cable with a male 3.5mm jack hangs out of the headphone, instead of slot built in to the headphone. There is a small piece of plastic that comes with the headphone that will make sure the cable doesn't disconnect from this, but I personally hate this design for removable cables, it never fills me with confidence that it won't break eventually.
Comfortability:
It's okay, earmuffs aren't usually super comfortable for me, they have to press hard for the sound isolation to work properly and my head is a bit big. After a few sessions with these, they got more comfortable. I do hate the rubber band thingy that self adjusts the height/size/fit of the headphones to your head, this really sticks in my hair and rips it out if I'm not careful when taking the headphones off my head. These headphones are pretty big, so taking them off and hanging around my neck, is uncomfortable, as the cups push on my throat and make breathing slightly harder
Conclusion:
They are okay, good for my use. A few negatives, a few positives.
I would buy them again.