There are four models attached here:

1.  Spool Mount

The spool mount clips onto the back of the Ultimaker 2 and allows various spindles to be quickly swapped in and out.  This can be useful if you have filament spools from different sources that all expect different diameter spindles.  

The spool mount is the most difficult part to print, and should be printed using supports.  I found that Cura's 'grid' style supports were too difficult to remove, but had success using the 'line' style of support structure.  Be careful when removing the supports, as it's quite easy to break the little mounting clips at the top of the part.

The good news is, you only need one good print of this part, and you're done.

Update - I recommend printing the 'v6a' version of this part, which reinforces the main clip making it both easier to remove the supports and sturdier when installed on the printer.

2.  49mm Filament Spindle

This part can be used to mount the official UM2 filament spools.  Like the original filament mount, this part is long enough to mount two spools concurrently.

Supports are recommended when printing this part.  

3.  38mm Filament Spindle

This part can be used to mount spools that expect a 38mm spindle size, as used by some Australian retailers.  It should print easily with no supports.

4.  31mm Filament Spindle

This part can be used to mount spools that expect a 31mm spindle size, as used by some low-cost Hong Kong retailers.  It should print easily with no supports.