Even after more than 50 years on the market, the binding system for plastic bindings is still considered one of the best methods for binding documents. The flexible and costeffective system meets the needs of most users, from students to professionals in large companies. Gives bound documents a professional appearance. Durable plastic binder spines of premium quality. The most popular, economical, and flexible binding method. 12 mm binder spines suitable for 56 to 80 pages. 21 rings, blue, round. Pack size of 25 pieces. Compatible with any plastic binding machine with 21 rings for binding up to 80 sheets.