My Gitane tandem also has the Atom drum brake hub with an 11mm axle; nice to know there is a possible replacement if the original fails (still working at this point). The freewheel is an Atom "Tandem" freewheel, with four pawls instead of the usual two pawls. I did have to ream my Phil splined freewheel remover slightly to fit over the 11mm axle, but it works fine.