Your envelope may weigh between 50 and 500 grams and the maximum dimensions are: 38 cm long, 26.5 cm wide and 3.2 cm high. Make sure it is not smaller than 10 cm long and 15 cm wide. That way the shipping label can be stuck on properly with the barcode on one side. The label may be folded over, but the barcode should not have any wrinkles or creases. This way it remains easily readable.