Spiral binding rings, also known as coil bindings or spiral coils, are flexible plastic or metal bindings used to secure sheets of paper together. They are commonly used in notebooks, presentations, and manuals for their durability and ability to allow pages to lay flat when opened. These bindings consist of a continuous coil that is threaded through closely spaced holes along the edge of the paper. The coil can be made of various materials, including plastic (such as PVC or nylon) or metal (such as aluminum), and comes in different diameters to accommodate varying thicknesses of paper.