Gears are applied in any fields of engine construction. Since quite a while there has been a trend for more compact and more powerful gears. The area of a circle grows with the square of its diameter. The capacity of cog wheels also grows by square with the module. This shows that nesting the gear stages delivers significant advantages with planetary gears in terms of construction volume and construction material utilization! You are saving construction parts and get a moment adjusted row of gears with less levels with a at the same time better distribution of gear reduction covering a larger field.