100 – 9.75″ x 12.25″ Stayflats Plus Kraft Mailers. For years, colleges and universities across the country have relied on our 5 PSK to send diplomas. The 9-3/4″ x 12-1/4″ size holds most standard size diplomas. Made from durable .028″ Tan Chip paperboard, it will stand up to the rigors of the mail. Keep documents from folding or bending without additional packaging or stiffeners. It’s also environmentally friendly and 100% Recyclable.