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If you choose to use your own paper, please check with the United States Postal Service (USPS) http://pe.usps.com/businessmail101/mailcharacteristics/cards.htm for requirements needed on postcard size and paper weight. The USPS says a good unit of weight measure is an index card. My favorite cardstock paper is #80 cover paper, available by the sheet at office supply stores such as Office Max, Staples or Office Depot.