11" x 13 1/2" White Self-Seal Flat Mailers. Strong chipboard mailers protect photos and documents during shipping. Manufactured from . 028 white chipboard. Light-weight to save on postage. No additional stiffeners needed. Peel and seal closure. Pull tab tear strip for easy opening. 25/Case.SHPRM3SS25PK. RM3SS25PK. Shoplet select Shoplet select White Self-Seal Flat Mailers 25 Pack.