50 12x16 Picture Mats for 8x12, White w/ Blackcore + Backing + Bag 50 sets of 12x16 picture mat for 8x12, White w/ Blackcore + Backing + Bag This item comes with 50 single mats, 50 backing, and 50 bags. The opening size is 7.5"x11.5" for 8x12 print. The mats are beveled cut with black core and 4-ply thick (about 1.4 mm or 1/16 inch).