Here you cross the "green border" between Austria and Switzerland. Even if the sign may seem a bit daunting, you as a biker are in no danger. And you will not have much to customs clearance in your weight-optimized tour bag anyway. ;)
The border between Switzerland (Canton of Graubünden) and Austria (State of Tyrol) runs somewhat unexpectedly through the Fimbatal. A sign indicates that the external border of the European Union is also located here. A border stone can be seen next to the path.