This premium plastic comb binding spine is for use with any standard 19-ring comb-binding system. These plastic comb-binding spines in black have a 3/8" diameter and provide a custom look to your official documents. The spines have a capacity to hold 55 sheets with its 19-ring comb-binding system and are sold 25 per pack. Number of sheets: 55. 25 per pack. Material: Plastic. Shape: Round. Use with any standard 19-ring comb-binding system. Gives a professional appearance to bound documents. Plastic binding combs. Easy to add and remove pages.