Postage

An important part of the card industry is posting. Here I have got a chart of postage sizes, prices and weights.

So here you can see here the depth of a standard letter is very small and will not be deep enough for the layers I will be using in my cards. For this reason I will need my cards to be a large letter which means that I can use up to 353mm x 250mm in width and height. This gives me more room for my designs than originally thought which is a bonus.