This custom designed keychain is CNC machined from solid naval bronze and then finished by hand. The craftsmanship, attention to detail, and material choice for this piece allow the minimalist design to have maximum impact. This keychain wrench has 2 sets of openings, one for SAE bolts and nuts and one for metric bolts and nuts. SAE sizes: 9/16" - 1/2" - 7/16" - 3/8" - 5/16" - 1/4". Metric Sizes: 11mm - 10mm - 9mm - 8mm - 7mm - 6mm. The wrench openings are precision shaped to perfectly hold and torque these common bolt and nut sizes. Naval bronze is extremely tough and highly resistant to corrosion. The diameter of this keychain is 1.75in. (4.45cm).