The bracelets are one size fits most, but the ends are slightly adjustable for a snugger fit. The pyrite bar on the bracelet measures 7mm X 38mm at widest point, and is 18k gold plated brass The pyrite is hand crushed and arranged so it may vary from the pyrite in the listing. Please note: it is normal for some flecks of pyrite to flake off over time with normal wear and tear. Mother Nature rarely duplicates itself so all pearls, quartz crystal and pyrite stones may vary slightly from listing.