Periwinkle Side-Loading Bubble Mailers – 27 Pack. Padded Envelopes; Internal Size: 12″ x 9″ (L x W); Self-Adhesive Flap: 2.36″. Lightweight bubble envelope, light parcel. Matte-coated bubble mailers to help maintain color. Side-Opening Bubble Mailers:Spacious loading opening with wide self-seal flap.