Need a file built for daily use? Oxford reinforced-top file jackets feature a sturdy 11-pt manila stock and double-ply reinforced tops, so you can have peace of mind knowing that the file folder is built to last. Easy thumb-cut access. Expandable to increase filing capacity. SFI Certified Fiber Sourcing. Tidy up your office with this letter-size, 8 1/2in x 11in, file jacket with 1 1/2in expansion. Manila file jackets come in a box of 50.