When I ordered these arches for my sons I was thinking of wooden train tunnels, but I was concerned because I wasn't sure how big they were and whether or not trains would fit. They are HUGE, the arches are almost 11 inches wide and 5.5 inches tall. The tunnels are nearly 11 inches long. They work well with the trains, but the children have used them to make airplane hangers, marble runs and all kinds of things. My husband feels like they take up too much room as they don't stack well, but with the other blocks in a large bin they fit well. They are durable and I would highly recommend them.