Won``t scratch, chip, peel or discolor. 19-ring plastic spines bind 11 x 8-1/2 documents. Editing capability with a machine. Compatible with GBC and other plastic comb binding machines. To select correct diameter, measure thickness of material (including covers) and add 1/8". Spine Type: Comb; Sheet Capacity: 55; Spine Diameter: 3/8 in; Number of Pins: N\A.