I was slightly surprised that the nib unit on the/my HongDian N8 can be unscrewed for removal so readily. Not so the nib units on the similar-looking N7 piston-fillers, which are fitted with plastic and not ebonite feeds.
That's a good thing, because even the larger HongDian EF nibs don't write finely enough for my preferences, and with this pen (of which, well, the price was right) I was stuck with an F nib. At least I can swap a spare HongDian EF nib unit into it.
The nibs in the N8 are indeed different from those in most HongDian fountain pen models that use the (often erroneously, or at least laxly, referred to as “#6”) relatively large — on the scale of smaller and larger — nibs; they are 35mm nibs, and not 32mm nibs each with a triangular cutout at the root of the nib body. (Yes, I pulled the nib and feed out of the housing eventually for inspection, out of curiosity; but that part of the disassembly just isn't shown in this photo.)