The popular Sabona Tudor Copper Magnetic Wristband contains a 1700 gauss samarium cobalt magnet is in each tip.   

Sabona Copper Designs are an attractive way to wear copper and magnets!   All styles are designed for comfort and manufactured to maintain shape and quality appearance. Sabona Copper Wristbands are made with the purest copper available-99.99%.  Sabona chooses Samarium Cobalt magnets for long term durability and rust resistant qualities.

 To get the best fit, subtract 1/2" to 3/4" from your wrist size to determine the size Sabona Copper Wristband you need. Sizes are Small (5.5"), Medium (6.0"), Large (6.5"), and Extra Large (7.0").  Wristbands are to be snug, but not tight. If you are in between sizes, it works better for the copper wristband to be smaller rather than larger.

Copper, when in contact with the skin, form chelates with human sweat (sometimes seen as a green deposit under the bracelet) and is thus absorbed through the skin. It can be removed with soap and water or lemon juice. To clean your Sabona bracelet, use a good jewelry cleaning cloth to keep the outside polished and the inside clean. 

For a sizing guide clink here : https://sabona.com/sites/default/files/SabonaWristbandSizingChart.pdf