Replacement Arm Pad Armrest For Office Chairs Arms. The smaller than average size of these arm pads insures less damage caused by striking the desk or other surfaces around your work area. Mounting holes are 4" to center. Pads are less than 1" in thickness. Dimensions: 8.75" long x 2.75" wide. Cut out area is 5.25" long x 1.7" wide.