This is a set of 100 black mini envelopes, measuring 12.1cm x 9cm. These were custom-made to your specified size and color. I'm not an expert on paper quality, but they have a good thickness and feel sturdy. They are perfect for holding memos, business cards, or for use as receipt holders in shops. Stamping with silver or white ink would look stylish. Bills fit inside when folded in half. *We can also discuss increasing the quantity.