How many World Cup shirts might not be worn in matches?

Up to 18 of the national team shirts released for this summer's World Cup could end up unused by their countries, following Fifa's decision over which kits will feature in the group stage. A total of 108 strips, excluding those worn by goalkeepers, have been released by the 48 teams taking part in the US this summer. But only 87 of them are guaranteed to feature at least once in the tournament. Every nation has at least two main kits, following the traditional 'home' and 'away' shirt concepts. …