Feature These bulk pin backs are made of nickel-plated copper, durable and rust-resistant. Smooth surface, sturdy design securely locks your pins in place, preventing them from falling off and replacing torn screws or wrench locking mechanisms; Keeps your items secure during important moments. Don't lose your pins—keep them firmly fastened with this convenient set. Small screw pre-installed for easy use. No loose parts to handle. How to use: Insert the black screw into the center hole, then use a small wrench to partially tighten one half of the black screw to secure it, attach the brooch or medal to be fixed through either end's small hole, then use a wrench to gradually tighten the black screw to ensure a firm hold. Item Type: Pin Keepers Material: Brass Color: Silver Type: A/B (Optional) Size: A Small 6x5mm B Large 6x9mm For more details, please refer to the photo. Quantity: 10 Sets Note: Due to manual measurement, there may be a 0-3mm size variation, which is considered normal. Additionally, due to differences in monitor displays, the actual item color may vary slightly from the image. Package includes: 10 Sets x Pin Safe Locks