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.