This is a simple yet surprisingly useful hook for RC cars. I made a few of these several years ago and didn't think much of it. Recently I've gotten some requests for more of them, so I thought I'd also share the design here as well. The rough wheel diameter is 105mm. I use them on my Traxis Slash and Temper 4x4. With some simple scaling, they could be adopted to work on just about any size car. Hope you find them useful.