1Diameter and Capacity: These binding coils have a diameter of 8mm (5/16 inch) and can accommodate up to 40 sheets of paper (A4, 70g), easy to add and reduce paper. 2Binding Specifications: These spiral binding spines have a 4:1 pitch, 48 loops design, which is compatible with any binding machine that punches 4 holes per inch. 3Plastic Material: These paper binding spiral coils are made of excellent plastic, with good toughness, wear resistance, aging resistance, and has a long service life. 4360 Degree Turning: These plastic spiral binding spines allow for 360 degree page turning rotation function, making your binding items flat and easy to read. 5Wide Applications: This kit includes 100 spiral binding spines, perfect for letter size paper (8.5x11 inch), widely used for binding paper, documents, manuscripts, etc. 100 x Spiral Binding Coils