Sabona Pro-Magnetic Sport Wristbands feature a combination of magnets and minus ion producing material. The silicone wristband has a total of four 1200 gauss samarium cobalt magnets, each positioned bio north facing the skin. Wristbands also contain a titanium material which produces minus or negative ions. Sabona chooses Samarium Cobalt magnets for long term durability and rust resistant qualities. Sabona Pro-Magnetic Sport Wristbands will stretch but snap back to the original size. You can wear them snug or loose, so choose your size accordingly. Sizes are S/M (7.0"), Large (7.5?), and XL (8.0?).