Compatible with standard wooden railroad sets- Brio, Ikea, Thomas & Friends, etc.Update- added a 90mm clearance support. Total height is 102mm; should fit on a Thing-o-Matic.Print and slide onto wooden tracks. Should fit snugly but not too tight.I've included three sizes measured by the clearance they give under the track. Hopefully your kid's cars aren't too tall- let me know and I'll do a 100mm- but that would be really pushing the max size on a Cupcake or ToM at 112mm total height.