Lead singer Alastair Britton said, "It's great to be asked to perform at the Foster's National Sevens at Cardiff Arms Park. We are regular performers at the Arms Park and we are always only too pleased to be involved with anything to do with the WRU and Welsh rugby.
"We will certainly be getting into the spirit of the Sevens event. I've heard there will be a lot happening on the day - including some hot tubs - and we will be looking to add to the whole atmosphere. We will be performing a good few well known covers and some of our own songs too. We love to get the crowd involved and I'm sure there will be no shortage of that next month."
With the 12 Principality Premiership sides participating on the day, including many of the Wales Sevens squad, plus the top two teams from the SWALEC Championship in Bargoed and Ebbw Vale, along with Welsh Students and RGC 1404, all is set for an action-packed day of Sevens rugby, with plenty going on off the field too.
There will be a kids zone with rugby skills workshops, face painting and more, while everyone who purchases a ticket in advance of Thursday 22 August will be entered into a prize draw to win a hot tub for five people to enjoy on the day.
The first game will kick off at 10.20, the Cup final is set to take place at 6.30pm, with live entertainment taking place throughout the day and into the evening.
Tickets are on sale now at just £10 for adults, £5 for Under 16s and £20 for a family ticket (2 adults, 2 children). Go to www.wru.co.uk/nationalsevens to purchase tickets or call 0844 8471881 (Ticketmaster) or 02920 230130 (Ticketline). Personal callers can also purchase tickets from the WRU shop, 8 Westgate Street or from Ticketline, 47 Westgate Street.