Hi, Zoran. The Hawks adapter looks to be about the same thickness as my other adapters when retracted, and then it extends out a few millimeters or so when turning the helicoid. It could be ever so slightly thicker than the Voigtalnder, but I don't have measuring tools capable of detecting the small difference. I think it just looks thicker, because the Voigtlander has more cut outs in the design, whereas the Hawks is more of a solid tube.
I've only played around with my C-Biogon, so far, but, with that particular lens, this adapter nails infinity when retracted.
I'm starting to feel a little stupid for buying 2 Voigtlander adapters for $180 each, considering how much more useful this Hawks adapter is. The only negative to the design is that there is a gap in the helicoid when extended that could let dust into the helicoid over time, but I'm not worried about it. I've seen some complain about a little bit of play in the lens, but mine is so minute that I didn't really even notice it. Maybe I got lucky with my copy?
p.s. I just threw on my Nokton 35/1.4, and it does well with infinity, too. It still may be slightly past infinity, but it is very close, and I'd have to test more thoroughly.