MIN CI 40 Pcs Super Strong Neodymium Round Silver Magnets, 18 mm x 3 mm for Dry Erase Board, Fridge, Crafts & More

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.

These magnets have extremely strong pull - they do not have adhesive on one side. They do not come apart easily - I found I needed to push them apart and that was a struggle. Their size is bigger than a nickel and are not quite a quarter inch thick.

Purchased these to make some fridge magnets. They were packaged well enough that no magnets were damaged. (Magnets can be brittle.) These are on the small side, but they are mighty! I was surprised how strong these were. I definitely recommend these if you need this size magnet. Good value. Worked perfectly for my fridge magnets.

Very strong magnets!

Nice and strong, works better than I thought they would. Have them in side a walk in cold box and freezer. I even ordered again, because they work so good and I need more.

I've bought other brands but this magnet seems to have better durability as it has a coat that's different than most magnets. It doesn't have that very shiny coating that chips easily with some force but because of that, I'm very happy with the quality. The edges are rounder also which I think helps to not chip or break apart easily. So one magnet was broken but not the end of the world as these in my experience are fragile at 3mm thickness. It's for my products so it is what it is. Not returning the product for one piece that's broken out of 30, either. I'm using this to mound it in a 6mm plywood drilling out 3mm hole using Irwin's 3/4" forstner bit. This magnet is just a tad wider but I use a wood block to seat it and seems to work well!

Almost all are great. One magnet was broken in two. It’s too much of a hassle to return them. The magnets are super strong

These are impressively strong for their tiny size. Great for DIY crafts, keeping small notes/photos on a board, or making custom magnetic closures. The pack quantity is excellent, and they’ve been consistent in strength and shape.

J’ai acheté ces aimants pour des projets de bricolage et j’en suis très satisfait. Malgré leur petite taille (9 mm x 2 mm), ils sont vraiment puissants : ils tiennent facilement plusieurs feuilles ou des petits objets métalliques sur un tableau magnétique ou un frigo. Ils sont bien emballés, tous identiques, et aucun n’est arrivé cassé ou abîmé. Je les ai aussi utilisés pour fermer un couvercle léger dans une boîte en bois, et ça fonctionne parfaitement. Attention toutefois : ils sont vraiment petits, donc à manipuler avec précaution si vous avez des enfants à la maison. Aussi, il faut parfois s’y prendre à deux fois pour bien les décoller les uns des autres tellement ils s’attirent fort. Bref, un excellent produit pour le prix, je recommande sans hésiter pour tous les petits projets créatifs ou pour organiser son espace efficacement.

Super strong, on time. and great for all things science.Great

I was impressed with these magnets. They are very small, but have a strong attraction. I am using these for lapel pins, and they hold through several layers of fabric without issue.

Very strong for their size!

la quantité qu'il me fallait pour mon projet