Update: Latest version fixes a customizer bug that hides the case hole size parameter. (Previously 133 downloads.)
This thing covers a larger hole in an enclosure while still providing space for a cable to fit. This is useful when you need to drill a larger hole in order to fit the cable ends through the enclosure wall but want to limit the overall size of the opening.
It's fully parametric and commented. There are 10 parameters designed to make it easy to customize for your application.
In the photo you can see that the hardboard is blown out (because I didn't have it supported properly when I drilled through it). Regardless the plug still works perfectly. I made the opening for the cable slightly larger than the cable itself so I could fit a few more small wires through it as well. It's very solid and holds very nicely.
I'm using this for an enclosure for one of my 3D printers to exhaust ABS fumes.
If you're building an enclosure and need adapters for exhaust tubes, try this thing: http://www.thingiverse.com/thing:38813
I use this as part of my parametric printer enclosure, which is available here: http://www.thingiverse.com/thing:39787
See the detailed comments for instructions on how to customize this.
The STL is rendered for a 0.75" case hole cut into 3.5mm hardboard, with room for cable(s) measuring 5.4mm in diameter. In my application, the 0.75" hole fits the ends of a USB cable, and the 5.4mm diameter fits the USB cable plus a few more wires for power.