Racedots bib holders are made from extremely strong rare-earth magnets in a thin metal shell. The patented design allows the two magnetic pieces to lock inside one another making for an extremely strong, hard-to-break band no matter what the fabric. No piecing or tearing your favourite technical tee, cycling jersey, or race suit. Racedots have a nickel plated copper shell, so they will never rust or stain no matter how much you sweat.