Hello Raphi. Unfortunately, the Smoker Box 480/570 does not fit your City420 gas barbecue because of the distances between the holders. They do not grip the edge of the gas barbecue. What I can recommend is this smoker box https://www.galaxus.ch/de/s4/product/landmann-raeucherbox-raeucherbox-raeucher-zubehoer-6190340. You can fill this smoker box with wood chips and place it on the grill grate next to your food.

Just saw the answer myself in the description, should probably fit 480/570, G/C