This is an idler with teeth to increase the ability to hold the tracks in place. If attached to a power source somehow they'd be able to drive the treads but that was not my intention (I'll be making one of those soon based on this design).

This is for: thingiverse.com/thing:35668

The length between points was found to be different than expected through trial and error.

Sorry - Had to update... it helps to double-check that the hub doesn't interfere with the gear part of it. Now fixed.

And one more fix - I should really test before releasing my items. hehehe. Adjusted outside diameter of teeth down quite a ways. Adjusted width of teeth up a bit and made angle a little better for printing.