400 – 6″ x 6″ Stayflats Plus Kraft Mailers. Our 9 PSK is an ideal mailer to send CD/DVDs and eliminate the need for a padded or bubble mailer. The 6″ square size holds CD/DVDs in a paper, paperboard or Tyvek sleeve. Made from .020″ Tan Chip paperboard, it’s an environmentally friendly way to store and send CD/DVDs. It’s also 100% Recyclable.