Some sides have opted for experienced, ageing squads, while other nations have looked for the speed and agility of youth to guide them through world rugby's premier competition.
The All Blacks have been revealed to have the most experienced squad at the World Cup, but that experience does not come hand-in-hand with being the oldest team, with enough youth injected into the squad to have New Zealand rank in a tie for sixth in average age, at 28.2.
Two of their main rivals for the Cup surprisingly have the exact same average age as the All Blacks, with South Africa and Ireland both having an average squad age of 28.2.
The Springboks have 14 players aged 30 or above, led by the ageless Victor Matfield (38), but also have good balance, with nine players in the squad younger than 25, including 21-year-old prospects Jesse Kriel and Handre Pollard.
Likewise, Ireland have five players older than 33, but have a core of players in their prime to give their squad a solid overall balance.
The oldest side in the competition is France, who have just one player under the age of 25 - promising 21-year old centre Gael Fickou. Although they don't have as many old-timers as the Springboks, the lack of youth in the squad shows how coach Philippe Saint-André is looking to use wise heads at the World Cup, with his average squad age of 29.2.
The Pacific Island nations also have squads with a distinct veteran tendency - with Samoa (28.9) and Tonga (28.6) having the second and third oldest squads travelling to the United Kingdom, while Fiji (28.4) are fifth.
The youngest squads? The two host nations, with England and Wales both have an average age of just 26.2.
England have 18 players aged under 27, with Stuart Lancaster opting for youth, including five players under the age of 23.
Wales meanwhile have 19 players 26 or younger, including players who have played plenty of tests such as Sam Warburton (54), Leigh Halfpenny (61) and 23-year old George North (50).
Will their youth policy play dividends, or will the calm experienced heads prevail?
There are just 13 days until the Rugby World Cup begins.
Average age of RWC squads:
1. France 29.2
2. Samoa 28.9
3. Tonga 28.6
4. Romania 28.5
5. Fiji 28.4
6. Ireland 28.2
7. New Zealand 28.2
8. South Africa 28.2
9. Canada 27.9
10. Italy 27.8
11. Japan 27.8
12. USA 27.2
13. Scotland 26.7
14. Argentina 26.6
15. Namibia 26.5
16. Australia 26.4
17. Georgia 26.4
18. Uruguay 26.3
19. England 26.2
20. Wales 26.2
