Museo #6 Standard 4-1/2x5-13/16", Two-Sided Matte, Archival Inkjet Artist Cards, 220gsm, 24 Pieces with Matching Envelopes, 14mil. 100% cotton, which has the highest percentage of alpha cellulose (the purest form of cellulose) Museo Artist Cards are compatible with most photo-realistic inkjet printers. No fluorescent whiteners added Two-side printable Use of naturally occurring pure Artesian well water