# System options in the system tree

> [HTML Version](system-options-in-the-system-tree.html)

Several options are available in the system tree under "Shafts" and "Bearings" using the context menu.

The context menu under "Shafts" provides following options:**(./images/optionsInSystemTree.png)**

- "Add shaft" adds a shaft to the system.If groups are used shafts can only be added to groups.

- "Add group" adds a group to the systems. 

- "Add coaxial group" adds a coaxial groups. The difference between coaxial groups and groups is, that coaxial groups only have an axial position and support elements can be used between shafts in different coaxial groups.

- "Add planetary group" adds a planetary group. A planetary group rotates about a carrier shafts and a number of planets can be defined on the group. All elements are generated "number of planets" times.

- "Add elastic part as housing" adds a 3D-elastic part as housing. This part does not rotate. See [3D elastic part as housing](3d_elastic_part_as_housing.md) for details.

- "Add elastic part as shaft" adds a 3D-elastic part as shaft. This part can rotate and it can also be a planet carrier. See [3D elastic part as shaft](3d_elastic_part_as_shaft.md) for details.

- "Import shaft system" allows to import an existing shaft system. Either a file of a MESYS shaft calculation can be selected of a file in REXS format.

- "Export shaft system" allows the export of the system in REXS format. This format allows the data exchange with other CAE software.

- "Export geometry" exports the system as STEP file. Only a simplified geometry is used for gears and bearings. The export could be used to check it it would fit into a housing for example.

- "Sort groups and shafts" sorts shafts and groups alphabetically. Initially the elements are sorted in creation order.

- "Set global markers" allows to define markers used in the 2D-view for example to mark bearing positions for a gearbox,

- "Add system" generated a cylindrical gearbox or a planetary gearbox.

The context menu under "Bearings" allows to activate or deactivate settings for all bearing calculations at the same time:

**(./images/optionsInSystemTreeBearings.png)**