These are replacement eccentric rods for MRC/Rowa 2-8-4 Berkshire steam locomotives.
They have all the detail of the original, and clip into the cup sockets on the bell crank and 3rd driving axle.
They come in a pack of 4 and is are available here.
The kits are printed in the Shapeways FUD material which will require cleaning upon delivery, please see my FAQs for more information.