This is a Large Rock that is composed of Two tiles.   It is compatible with all of my other Modular RC Course tiles.  All my hexes are designed to use 4x6mm round magnets, they just push into the holes.

The b set has an additional keyway in the rock, I have not printed the b version.  

This set is designed with my new V2 Tiles, these have a keyway that allows a 3d printed "key" to be used to help lock the tiles together. I'm working on a press in key but right now it slides in and this makes it difficult to use on all sides at the same time, but it does help stabilize the set and reduces the need for the magnets.

These are 240mm wide at the widest point, they can be scaled to whatever size your printer is and should not cause issues.

The white truck is 18th scale and the blue truck is a 16th scale WPL.