Our pre-cut 125mm Square cardstocks fit perfectly into our 130mm envelopes so this incredibly useful cardstock size is the key to your flatboard RSVP's, evening invitations, thank you cards, little menus....all sorts of stationery items! To create double layered stationery with a thicker 'feel' and 'border' why not team with our 119mm square cardstock printing details on the smaller sized card. We always say, "start with the envelope and work backwards" which is why our Enfolio elements are so carefully considered and sized accordingly. 125mm sqare is a nice size and would be perfect for flatboards day invitations too. If required several loose card squares could sit behind one another if additional information was required but just keep the font size in mind and go for a larger size (147mm square) if the volume of text in any additional information makes the font size rather too small to read.