When I was a (younger) child I used to play a lot with my Lego train. Today my own children not only play with my old (blue/grey) Lego train, but also with the new (dark grey) Lego train. While the track gauge is still unchanged, unfortunately the new tracks have a highly sophisticated, incompatible type of connection. This adapter allows to connect old and new Lego train tracks. It also interlocks well on top and bottom with basic Lego bricks. The adapter can be printed without additional support structures. The STL-file already includes support for the one-and-only unprintable overhanging part. This support can simply be broken off after printing.