Fellowes 42mm 5:1 pitch metal binding spirals in black (25 units) 5112001 provide the necessary capacity to compile exceptionally thick projects. This pack of 25 units in black metal, 42 mm in diameter (5:1 pitch), allows you to bind up to 390 sheets of A4 paper with complete security. Its robust metal structure protects the printed core for years of use. Perfect for institutional archives and university compendiums.