RAYSON wire coil binding spines are built for durability and ease of use, making them an ideal choice for binding reports, presentations, and documents. Crafted from high-quality metal, these black coils enhance document longevity and allow them to open flat and rotate 360 degrees for easy reading and copying. With the ability to bind up to 40 sheets of 20lb paper, these coils are perfect for smaller to medium-sized projects. The margin size affects capacity, with a 2.5mm margin recommended for 40 sheets. Designed for 4:1 pitch binding machines (4 holes per inch), these coils are incompatible with 3:1 pitch systems. These versatile black coils work with any 4:1 pitch pre-punched paper or wire binding machine, making them suitable for professional use at the office, school, or home. Each pack includes 100 coils, with 48 loops per coil, suitable for Letter and A4 size sheets. Excess wire can be easily trimmed as needed. RAYSON wire binding coils are clean, durable, and ensure secure binding. Whether using a RAYSON binding machine like the PD-1501, PD-1503 or binding by hand, these coils simplify the process for efficient results.