So this is a complete forearm assembly. It is still looking pretty clean because there are no wires but once it is wired up wires will be visible. 

Joint 6 is 5:1 planetary reducer. Joint 5 is plantery 6:1 and join 4 is 6.5: 1 bevel gear + HTD M5 belt. 

as you can see here joint 5 is using a 2:1 bevel gear reduction and after that 3:1 belt reduction. Total reduction is then 6:1.