Arneson Twin Drive. It's a semi scale model of the Arneson ASD15 in scale 1:30 which I did for my Canados 90 open (Hobbyking "Princess") to change from single drive to twin drive. It's not for high speed set up but for realistic scale drive.
It can be used like the old Graupner Hydospeed drives, a pair of 4mm shafts connected with a kardan coupling.
Standard sinter- and ball beraings fit into the drives.