Specification: Material: 304 stainless steel Quantity: 100 sets < p> Size: Screw size is about 4 x 3.8mm Top size is approximately 5 x 6 mm Product Features: Durable and rust-proof, corrosion-resistant. Easy to use: use a drill to drill a hole of the same or less than 5mm on your book or leather, then install two parts of the two sides to achieve the binding effect. Note: - For good binding effect, the hole on your book or leather should not be larger than the diameter of the screw studs (5mm). - Small parts, please keep it away from children. Scope of delivery: 100 x tops 100 x screws