Poly Bubble Mailers Self Seal Ships Fast and Free from New York Exterior size: approx. 4.25 x 6 inches (folded); 4.25 inches x 7.25 inches (unfolded) Usable size: approx. 3.5 x 6 inches “PACK” indicates number of mailers Quantity = Number of Packs For Example,If Pack = 10 and Quantity = 2, you are ordering 20 envelopes.