I made a couple of different ducts to tidy up the wiring under my Ultimaker. Of course you could use these for other general tidying up but that was the original purpose for them.
These are fairly short at 72mm due to warping issues but if you need longer ones (in multples of 12mm to make it easy for me) let me know and I'll upload other versions.
Make happy noises about your cables being tidy.
I included "mouse ears" on these to help prevent warping, a couple of quick slices with a sharp knife gets rid of them.