Jumbo set of folded cards and envelopes made of natural cardboard, 50 cards and 50 envelopes in square and DIN format, 100 pieces in one set, ideal to design yourself : Amazon.co.uk:
Square Recycled Kraft Cards and Envelopes Various Sizes
Vaessen Creative Small Square Florence Envelopes for Greeting Cards, Kraft, Set of 25, Matching Cards Available, Brown,3.7 x 3.7 inches
100-Pack 14 x 14 cm Square Envelopes, Brown Kraft Paper Envelopes for Greeting Cards, Wedding, Birthday, Anniversary Party Invitations, Sturdy and ...
25 Blank Cards With Envelopes A6 Rectangle or 6x6 - Etsy UK
KRAFT CARD Square Cards & Envelopes ~ 13.5cm x 13.5 cm (10pk, 300gsm)
5 x 5" Square Kraft Card Blanks 280gsm Envelopes 120gsm For Wedding Invitations
docrafts Papermania Square Recycled Kraft Cards and Envelopes (Pack of 50)
Kraft Envelopes / Cards Square 3.25 X 3.25 Handmade Wedding Guest Book Alternative Kraft Cards Small Little Rustic Stationery Set Paper - Etsy UK