These headpins are made from sterling silver (SS aka .925 is 92.5% silver) and are generally tempered half-hard for cleaner and smoother bends and loops right out of the bag. Wire diameter is measured in American Wire Gauge (AWG).
22 GA/.025"/.65MM - HEAD DIAMETER 1.5-1.6MM
24 GA/.020"/.5MM - HEAD DIAMETER 1.2-1.25MM
26 GA/.016"/.4MM - HEAD DIAMETER 1MM