the mongoose black diamond double has them 12X150mm maxle in the rear and 20mm maxle in the front. i have a double and it works great. super easy to take off with all the benefits of the allen wrench kind.
oi zonkou, it's the rear cassette freewheel set up that limits the axle size. as the cassette is the limiting factor (international standard) the freewheel system has to have some bearings in it to work and therefore you end up with 12mm axle. any bigger and the bearings become poor quality.
look at www.hartlett.co.uk for an alternative to the maxle (especially if you live somewhere with a modicum of mud)
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