I've used a couple of superlux headphones before and these did not disappoint.
I use these at band practice and sometimes even when I'm mowing the lawn, because yes they isolate the noise pretty well.
These are pretty big, so you might look a bit weird out in public with these. The cable is really long and can't be replaced if it breaks. Also when you're using these with a phone or something like that, you'll have a lot of cable that you need stuff somewhere, and it's quite annoying.
For me these headphones are bit too small, the cups fit over the ears just fine, but the headphones are really tight on my head, and the self adjusting band is at its max at all times. I don't really have a big head, and no other headphone has had this issue before. Though our drummer got one of these as well and for him they fit just fine, so keep in mind that these might not fit that well.
For the sound, the bass is nice and overall it's decent, It's not the best, but for the price really good.
Build quality is plastic, but it's superlux which means it's somehow really durable.