100 – 9″ X 11.5″ Stayflats Plus White Mailers. The 2 PSW is the same size as one of our original Stayflat Mailers. To this day, it is the standard size in the industry to send 8-1/2″ by 11″ photos. Made from durable .028″ CCNB paperboard, the protection of your important photos is assured. It’s also environmentally friendly and 100% Recyclable.