1[High Capacity] The plastic spiral binding coil has a diameter of 38mm and can hold up to 310 sheets of paper (A4, 70g), allowing for easy addition and removal of pages. 2[4:1 Pitch Compatibility] The spiral binding coil features 4:1 pitch, making it compatible with any binding machine that punches 4 holes per inch. 3[360 Degree Rotation] With the ability to rotate 360 degrees, this binding coil allows for effortless page flipping and reading, making it easier to work with bound projects. 4[18 Pcs Set] Each pack includes 18 spiral binding coils, ensuring long term productivity for all your binding projects, enabling you to effortlessly bind papers and store them securely. 5[Versatile Application] Ideal for letter sized paper (8.5 x 11 inch), the length of the spiral coil can be easily cut with scissors. Perfect for engineering documents, business projects, office documents, and university presentations. 18 x Spiral Binding Coil