sentences:  The stamps may be combined for more expensive tariffs.Sweden issues two forms of NVI valid for letters within Sweden of up to 50 g. These stamps may be combined when the weight of a letter exceeds 50 g. For up to 100 g – use two stamps; for up to 250 g – use 4 stamps; 500 g – 6 stamps; 1 kg – 8 stamps; 2 kg – 12 stamps.There are no longer surcharges to bulkier letters.