Our Magic Envelopes are large 9″x12″ Tyvek envelopes. Tyvek is a very sturdy and reliable material, so our Magic Envelopes can usually hold hundreds of receipts depending on the receipt size. However, if you find that your receipts do not fit, feel free to get your own envelope and stickytape the Magic Envelope on top.  This will cover postage costs and otherwise enable your package to be treated in exactly the same way.