Avid Rollamajig

[Fabian]

This dirt cheap method of reducing cable friction to early model rear derailleurs works surprisingly well; significantly reducing friction and noticeably reducing thumb pressure when shifting up gears, as well as making the down change much easier for the rear derailleur.

It's a must have item; depicted in the photos and described in the video below the photos.

 

[KCvale]

It's a must have item; depicted in the photos and described in the video below the photos.

Spiffy cable router but you really should work on your 'Must Have' list as it is getting ridiculous bud ;-}

 

[Fabian]

No question about it, the Avid Rollamajig is a must have item, for when you've installed one, you'll never go back to the dreaded extra length and extra friction of standard cable routing.

Throw one on your bike and you'll be just as enthused as i am, because it gives reliable gear indexing up and down the sprocket set.
The difference is night and day, but the design isn't new; being incorporated into early Shimano rear derailleurs like the Nexave Megarange and the current generation of Shimano Tourney rear derailleurs.