Heavy duty mailing box 310x220x76mm pk10 heavy duty mailing box 310x220x76mm pack of 10 7273201 heavy duty mailing box 310x220x76mm made from strong corrugated board this mailing box can withstand the toughest of journeys the quick and easy fastfold pop up design allows for almost instant use the strong adhesive self seal strip creates a secure closure to keep contents safe during transit and a simple tear strip allows for easy access when it arrives at its destination pre printed addre