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From an otherwise good set of A Class Vectra D2 wheels.
Think Spez hubs have a free hub like that.
I've fitted a few for a friend. it was a ddg hub from supercycles in Nottingham, the same people who do onza trials stuff.
be careful though, there are 2 types that are not interchangeable.
Upon removing it I found it was one of these, regardless of what Google searches threw up.
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The first pic looks an awful lot like the Formula freehub for the rear hub on my Salsa fat bike... ended up buying one from the US as ISON Distribution in the UK were so vague/useless!
http://www.bikeman.com/FW8840.html
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Second pic down looks like a Campagnolo to me.
A bit, the Campagnolo ones have 'very' mechanical pawls and the splines for the cassette are very deep.
Looks like a novatec free hub to me they general come in 12 mm and 15 mm axel types. The 12mm has cup and cone style adjustment flats and the 15mm uses 5mm allen key end caps.