Communicate your ideas with professional polish. 19-ring plastic spines won`t scratch, chip, peel or discolor. 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". Global Product Type: Binding Spines-Comb; Binding Spine Type: Comb; Sheet Capacity: 55; Spine Diameter: 3/8 in. Combbind Plastic Binding Combs