Very strong magnets. It seems overpriced for such a small amount of actual weight, but for me it saved hundreds of dollars of dumbbells. I have cast iron hex head dumbbells in 5lb increments up to 30lbs and then 30 to 100lbs in 10lb increments. These magnets allow me to hit the 5lb increments 35, 45... to 105 which saves me an incredible amount of space and money for dumbbells that I would only use infrequently anyways. I decided to keep the 5lb dumbbell increments under 30lb because the magnets don't stick that well to the smaller dumbbells. The magnets stick really well overall but if the surface is rounded or uneven they might not stick as well during quicker movements. For most of my dumbbells it's fine, but there are some i have to be careful about where and how I stick the magnet.
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