Archival Methods 16x20" Mat and Presentation Kits, 11x17" Print Archival Methods Window Mat Bevel-Cut - 1/8" Acid-Free Foam Board Backing - Crystal Clear Bag with Self-Adhesive Closure - Clear Mounting Corners - Tyvek Tape - Archival Methods Warranty Material: 4 Ply Bright White 100% Cotton Museum Board Mat Size: 16x20" / 40.64x50.8cm Print Size: 11x17" / 27.94x43.18cm Opening Center: 10x16" / 25.4x40.64cm