4Pack Stainless Steel A4 Notebook 3-Ring Binder Mechanism D Rings Loose Leaf Binding Spines Combs for Organizers Planners 3-Ring Mechanism- You will get 4Pack. The letter metal ring mechanism about 1.08 inch(2.75cm) wide, 11.02 inch(28cm) long, 1.18 inch(3cm) thick. Hole size is 0.22x0.16 inch(0.55x0.4cm), 0.79 inch(2cm) inner diameter. Screw and Nut- There are 8 sets. The screw size is 0.30x0.31 inch(0.75x0.8cm), pin 0.11 inch(0.28cm), nut size is 0.14x0.31 inch(0.35x0.8cm), 0.11 inch(0.28cm) inner diameter. Reliable Material- The ring mechanism is made of Stainless Steel, which are waterproof, rust-proof, not easy to break, durable and reliable, they can be applied for a long time. Easy to Use- The loose binder ring can be expanded and closed easily to add or remove pages, convenient and flexible to use for study. Application- This 3-ring binder mechanism is applicable for A4 size notebook.