AH are doing this offer again. You can only buy the vouchers in store from the 12th March until the 18th march ans from 2nd April until the 8th April. They are valid up until the 17th June this year
Day cards can be used to travel throughout the NS network for one full day and normally cost €48 per person so this is a great deal.
If you need some then as usual I can be persuaded to buy them for you and send you the codes by e-mail.
Please note that these are for off peak travel so after 0900 weekdays and the whole day on the weekend.