Another part - T-shaped cross his racing track and he is so happy. This is my design, works fine for us. Compatible with Hot Wheels tracks. Nice, smooth and sturdy. Fits up to 2 pcs per printing plate 256x256x256.
This one also has my latest revision of the connectors.
Be careful when removing the supports from the inside! I did it by sliding a razor blade first, to detach them from the model - see the photo.
I am constantly adding new parts to my boy's set and I'm more that happy to share the models with you guys, so enjoy.
Other compatible parts in my profile.
Hope that helps your kids too! :)