High Quality: This magnetic rings are made of premium aluminum, durable and sturdy. Anti Slip: This magnetic screw rings can lock screw tightly to reduce unnecessary slip. Universal: The inner diameter for this screw rings are 0.25inch, compatible with most shank screwdriver bits. Easy To Use: This portable magnetic rings are easy to use and remove, you just need to insert the screwdriver bit into the magnetic rings. Wide Applications: This convenient magnetic rings are widely applied in furniture assembly, hinge installation and fixed pendant, etc. Specification: Material: Aluminum Size Chart: Outer Diameter: 15mm/0.59 Height: 23mm/0.91inch Inner Diameter: 6.35mm/0.25inch Package Includes: 3 Pieces Universal Magnetic Rings(3 Pack) Note: 1. Please allow slightly error due to manual measurement. 2. Due to the difference between different monitors, the picture may not reflect the actual color of the item. 3. Wish you a wonderful online shopping!