15 - Premium White Acid Free and Archival Quality ATC Envelopes. A perfect size for Artist Trading Cards as seen in the picture. The chipboard in the photo is the true dimension of an ATC, so you can see how roomy they are for bulkier artwork. The envelopes measure 2 3/4 in. X 3 3/4 in. and packaged in a clear crystal bag. You will receive 15 envelopes per package.