Since official H2D nozzles are seemingly perpetually out of stock on the official Bambulab store (all except for 0.4mm at the moment), I notice that amazon is well stocked with what I presume are knock-offs that look just like the real thing:
Also, if you buy two instead of just one, then the price is well below what Bambulab is asking for theirs.
Most likely it is brass as why else would they specific mention it.
They might be good you need to try and risk it.
But this brand has some reputation in the 3d world
biqu has nice hotents being better then the original.
Haven’t used it myself but you can try.
I was lucky that my second hand 700 hour printer came with 3 extra hotends.
As per your suggestion, I just now checked the biqu website, but it doesn’t show any H2D hotends or nozzles. Just the blue build plate.
I think it’s both. Brass for the hotend, hardened steel for the screw-in tip.
Is that also how official Bambulab hotend-nozzles are built?
I tested the HF aftermarket nozzles and they were not good. With OEM HF I got around 60mm³/s. With the aftermarket HF it failed at around 40mm³/s and the printer threw an “extruder motor overloaded” error. I tried multiple times with the same results, I would stay away from them. They are probably using a cheaper material for the internal CHT and possibly simpler machining on the internals that is causing the motor to overload.
Agree, not worth taking any chances are these cheap ones. Volumetric speed of 40 is what i use now on my stock hotends (had to do a volumetric speed test). Have not tested my genuine BL HF hotends yet. 
My printer was expensive, I’m not risking putting a cheap knock off nozzle in it.
Used some already for normal printing its okay not tested it fiber filament.
Also Tpu its clogging very quickly its because of the detachable tip.
Not a Biqu, but I bought a cheap hotend from amazon (au) and so far it’s performing better than my bambu ones did. Bambu hotends were clogging up on longer ironing jobd, this one doesnt.
