5 different sizes for your interest: Binding screws are 5 lengths: 6mm, 10mm, 12mm,15mm and 18mm, all chicago mounting screws are 5mm diameter which fits most objects High Quality: The chicago screws are made of quality carbon steel, plated with silver nickel, sturdy and anti-rust, easy to bond, install and remove, these chicago nuts can be used repeatedly with good tightness Wide Application: The screw rivets are especially suitable for leather craft decoration, bookbinding, document, book, album, DIY crafts, etc Easy to install: Just use a drill to make a 5mm diameter hole, and install the 2 pieces on each side Convenient storage: We offer beautiful plastic storage boxes. So you don't have to worry about losing some rivet screws, so you can use them again Package includes: 16 sets of chicago screws (5 x 6mm) 16 sets of chicago screws (5x10mm) 16 sets of chicago screws (5x12mm) 16 sets of chicago screws (5x15mm) 16 sets of chicago screws (5x18mm) 1 x Transparent storage box