Heavy-duty tough expanding files are virtually indestructible. Double thick front and back panels with heavy reinforcement liner board for added durability. Tyvek® reinforcement at the top and bottom of gussets for extra strength. Gussets extend into front and back panels twice as far as standard files. Choose from alphabetic (A-Z), daily (1-31) or monthly (January-December) preprinted indexes. This product was made using wood sourced from a certified managed forest.