Keystone Tunnel

This is an HO scale tunnel entrance, but it can be scaled up for pretty much any model. It is a keystone type tunnel, and when I built it I inscribed numbers on the keystone like shown in the pictures. However, the model I included here has the numbers left off so you can add your own designations, or none at all. I also used PLA to print the tunnels and airbrushed them to have a weathered stone look. One piece design, so you shouldn't have any problems with assembling them.