It feels like a moment, like a match never before.
Wales are on the verge of qualifying for a major tournament for the very first time, while the Republic of Ireland - who qualified for the last World Cup - are aiming to get to a Euros for the first time.
The prize for the winner: a place at Euro 2025. Pretty special.
So a straight fight over two legs. Yes, Wales and the Republic of Ireland have been here before - not long ago, in fact.
Wales dramatically and heartbreakingly lost a World Cup play-off final against Switzerland, missing out on a place at the 2023 World Cup, while Ireland beat Scotland in their play-off final, thus reaching the World Cup in Australia and New Zealand.
For Wales, the women's game is growing and gathering pace, which at times is hard to keep up with. Being in the Wales camp this week, though, just feels different. Something special, something very big on the line.
A record will be set for a crowd watching a Wales women's home game. In excess of 15,200 tickets were sold days ago to beat the previous record but there is an expectation it could rise to 20,000 by kick off.
That record has been set not only because the Wales women's team have improved in recent years, but because the girls' and women's game in Wales has engaged with the senior women side and the various clubs they play for in the WSL, Championship and NWSL in the USA.
Chief among those well-known names in the Wales side is Jess Fishlock, a veteran of the game who keeps on delivering for Wales when she returns from America to represent her country.
Loved and admired by her team-mates, she also has a humility - even though she is a superstar of the women's game - where her team-mates refer to her as 'Just Jess'.
Ireland have perhaps more experience than Wales. One of Ireland's stars Denise O'Sullivan epitomises that with well over a century of caps and a club career thriving at North Carolina in the NWSL.
However, both managers - Rhian Wilkinson for Wales and Eileen Gleeson for Ireland - seem to have compared notes on what to say ahead of the match. "It's two very even sides, too close to call," they both admitted.
The rankings suggest they're not wrong, with Ireland 24th and Wales just five places behind. Both have been regularly climbing those rankings of late.
Although missing Chelsea's Sophie Ingle through a long-term ACL injury, there are no significant injury worries among the 26 players selected by Wilkinson.
Wales - justifiably - are confident, however they know a two-legged tie against Ireland will end up being a tight affair.
The importance of a good start and preferably a good lead from the first leg, which of course will be played in front of a Wales record crowd in Cardiff, will help.
But overconfidence will be something the squad will avoid through respect for their opponents, a team who have already been to a major tournament - unlike Wales.
Don't apply much significance to Wales' 2-0 victory over them earlier this year - both sides will be different for the play-off final, in personnel and attitude.
Perhaps the greatest significance of this game is a comparison between the relatively recent past and now.
In 2011, Wales hosted the Republic of Ireland, a game played in Newport. There were 400 people watching.
Thirteen years later, Wales Women play on an equal stage to their male team-mates at the Cardiff City Stadium, with 20,000 people paying to watch.
More, as always, to be done within the girls' and women's game, but clearly something has changed.
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