SKILCRAFT® - NSN6006974 Add extra storage to your classification folders so you can store all your project materials. Retention envelope/jackets measure 9" high and can be used with letter-size or legal-size classification folders. Each envelope includes a 1" capacity fastener and two legal-size holes and two letter-size holes that fit over prongs on legal-size and letter-size classification folders. Retention envelopes are made using 20 percent post-consumer material.