I believe these burn in stuff back then, but after I joined a few manufacturer jobs, this thing is kind of myth, because most of the stuff already tested at least certain of times before you can even buy it, and the burn in effect, is actually how your ears start to adapt the headphones imo, that product doesn’t do anything at all even you burned in whole day. Unless you are buying some really antique 2nd hand headphones like 10 years not in use, then a little burn time to reactivates the components is makes more sense