Let me start by saying that I have purchased dozens of this type of magnets over the years and am fully aware of their limitations. These are the first that I have purchased that have cracked so easily. I lightly tightened the mounting screws and two or three of them developed cracks. Hopefully they are glued to the cup and the pieces won't fall out. They are fairly strong but I highly doubt that they have 100 lbs of pulling force that they claim.
50Pcs Strong Neodymium Magnets With Hole & Mounting Screws - Heavy Duty Rare Earth Disc Countersunk For Locker, Tool Storage & Crafts
31 Review
50Pcs Neodymium Magnets With Countersunk Hole And Stainless Screws - Strong Rare Earth Magnets Disc For Locker, Tool Storage, Crafts By MIKEDE
42 Review
Power Up Your Projects With MIKEDE Cube Neodymium Magnets - Super Strong Rare Earth Magnets For Science And DIY
31 Review
Powerful Neodymium Bar Magnets With Double-Sided Adhesive - Ideal For Home, Office & Scientific Uses - Pack Of 16 Magnets
40 Review