Question about Heather's new cards in shoppe

Ok I have a question about Heather's darling new cards...what do you do about envelopes? I looked and the "invitation" size envelopes don't fit, the small ones don't fit, nor the business envelopes...so what do you mail them in??



They are sooooooo darling...but I need them mailable...

They're 4x6 so they should fit in an A6 envelope, something like this: A6 envelopes.

Thanks! Wasn't familiar with that size...