MIN CI 40 Pcs Super Strong Neodymium Disc Magnets, 18 mm x 3 mm Small Magnets for Dry Erase Board Whiteboard Office Fridge Crafts, Mini Round Rare Earth Magnet s for Building Scientific Models

I have worked with quite a few ultra-powerful neodymium magnets in the past 3 years, some of which are outright dangerous if handled recklessly, such as strong enough to crush fingers that get in the way, or outright lift refrigerators and small steel engine blocks. This is not one of those kind of magnets, but I still treat all neodymium permanent magnets with respect for safety.This was the perfect size to replace the anemic weak magnet in the antenna for a cellular network access "fail-over" device, so it would stay put on a vehicle or in a portable application in high winds.The original antenna underwent "sudden violent separation" from a car roof, followed by high velocity contact with the highway surface and dragging by its attached coaxial cable, accompanied by multiple secondary impacts with pavement and the side of the car until the driver was able to come to a stop after about 400 feet. Pieces of debris from the antenna base were recovered from the highway, bagged, and taken home to see if there was any hope of repair; not due to the cost - only a $25 antenna - but the 6 to 8 weeks of supply chain delays to acquire a replacement.Following examination of the debris, it was quickly determined that the tiny magnet used in the base during manufacture was woefully inadequate to hold it to the roof of a vehicle at highway speeds.A small mold was made to replicate the shape of the plastic base, the recovered fragments were placed approximately where they would have been before the accident, the metal parts were verified to still have electrical and RF integrity, and a small amount of resin was poured to reconstruct the base.The steel cup in which the original magnet had been placed, was measured for inside bottom diameter, as was its depth with a machinist's gauge. With sufficient cup clearance calculated to maximize magnetic field strength out of the bottom, these magnets were selected and ordered as the best fit and likelihood of sufficient strength to upgrade the base holding force to an acceptable performance level in the field.While the magnets were en route, the antenna system was tested with a rather expensive microwave antenna and feedline analyzer, and determined to be still functional within the cellular 4G spectrum.The empty cup was filled with JB Weld epoxy (which although it contains steel powder and is slightly magnetic, does not divert more than a few percent of magnetic flux). This was used to "pot" the magnet so when removing the modified rebuilt assembly from a car roof, it will stay firmly attached to the antenna and not the car.24 hours later once the epoxy had fully cured, the repaired unit was placed on the car roof, with a camera anchored nearby to observe it. The antenna analyzer was connected to the coax, and set up to monitor impedance and reflected energy in the center of the 4G cellular spectrum, and the unit was taken on a test drive.The first leg consisted of about 2 miles of incredibly rough dirt road, which subjected the unit to extreme vibration, which should induce microscopic very fast separation and gap closure over millisecond intervals, which can cause data errors and "chopping" of voice over IP. The magnet was strong enough no significant signal degradation was observed.The second leg was about 4 miles of secondary road at between 35 and 50 mph. The final leg was 10 miles out and 10 miles back of highway between 75 and 80 mph to observe aerodynamic behavior and the magnet's ability to overcome these forces.The magnet passed with flying colors.Most people won't use them for this, but it worked well. I'm going to put another one in a TV remote so it stays put on a steel cabinet when not in use, and the cats can't hide it under furniture.

Love the build quality, super strong and magnetic problem is their hard to get off the stack once you can separate them they work wonderfully. Require super strength to remove them because they are sent vertically stacked and the magnet is so strong. They’re trying to get each magnet off, requires gorilla like strength, which is simply reflective of the degree of magnetism they possess.

These magnets work as advertised. Very strong magnets that if you have a particular need for them will likely work for you. My fault for not checking their size. Were smaller then I expected. They still got the job done. I ordered them before that were about quarter size. Those were easily broken. The ones I bought this time were little smaller then a nickel and do not deem as fragile. I will be ordering more. If only to have in my shop to use as needed. They difficult to separate. Just slide them to get them apart. Truly amazes me how strong they are. No regrets buying. Money well spent.

I've started to make some 3D printable toolbox organizers. They need the strongest magnets available to work over liners and keep tools from sliding around when opening/closing drawers. I had some strong 10x3mm magnets that worked great, so I designed the holders with pockets for that size magnet. These magnets are the same size as my old ones, but only a third of the strength. It held up about a pound from the tip of a wrench. (And would hold more weight if using the full surface area) Wich is pretty good for most applications. However, the old magnet held about 3lbs and that's what I was looking for.I spent many hours going through all the 10x3mm magnet reviews. This is one of the only ones that didn't have people complaining about the thickness being around 2.7mm instead of 3mm. I wish all sellers were required to list the actual dimensions (not just pictures of a micrometer showing the advertised dimensions) and the N rating of magnets. It's hard to believe no one on Amazon sells true 10x3mm N52 magnets.

Wow these suckers are STRONG!Well built, light weight and definitely very strong magnetic hold. They'll be more than enough for the project I have in mind.These things will most likely be permanent if used as is. If integrated into a fridge magnet with JB Weld or 3D printed within one, they'd be removable. Otherwise, a tool would be needed to pop it off the surface it attaches itself to.

working fine for the reason I bought them. Good strong little magnets.

These look good and are consistently sized (some are a little thicker than others but not by much). They stick to each other VERY well. But, they don't stick to metal as well as I hoped. I attached one to a 1.6 oz flashlight and it stayed on a vertical steel surface (file cabinet, shelf support, refrigerator), but could easily be pulled away or slid. I attached one to a 5.5 oz flashlight and it slid down. I used one to hold paper to the refrigerator - it held 1-3 pieces well. But, when I pulled the paper, it easily popped off the magnet letting it (the magnet) fall to the ground - a stronger magnet might allow that paper to be pulled out, but the magnet would (usually) stay stuck. I probably wouldn't use it around kids as it's too easy to pop it of a metal surface. And small magnets and kids are a bad mix anyway...

These are the best magnetics, extremely strong. I am using them in leather bookmarks, money clips. These are also great when you use magnetic paint ( especially on a wall) to hold up photos or artwork!