As a teacher, I need mighty magnets that can hold up multiple posters at a time. These are the best. Super sturdy and effective. I have recommended them to multiple teachers. They are the best thus far!

Advantages:
(1)These very strong magnets will easily hold a heavy calendar on an iron-alloy wall.
(2)The parts of this product that people would normally look at are attractive.

Disadvantages:
(1)The biggest disadvantage is that the neodymium magnet underneath is not nickel-plated and so it looks black and ugly.
(2)The magnet underneath has a bolt in the center, which cannot be loosened and should not be loosened.
(3)On approximately 2 of the 4 magnets, just underneath the top of the black plastic knob, there will be black plastic debris which the buyer might very likely want to remove. A Revlon Cuticle Cutter will not be able to get into the correct angle to clip it off. A long nose pliers or tiny scissors could be used. However, I've found that simply moving my index finger back and forth for about 30 to 60 seconds is the best way to crack away this 1 hanging, unwanted debris.

Discussion:
(1)The diameter of this product is 1-3/8" and the height of this product is 7/8".
(2)Other magnetic products that can be used to hang a heavy calendar on an iron-alloy wall include any eyebolt magnet and also the Learning Resources brand "Super Strong Magnetic Clips," which are sold as a set of 4 colors. Plastic clips with tiny neodymium magnets attached to them tend not to be strong enough to hold a heavy calendar on an iron-alloy wall unless the plastic clips are glued to the wall; their plastic jaws would be strong enough to hold the heavy calendar.

These things work.

I got them to use as a handle on the door for a key box in our office. The door is light and is only locked once per day, but it is very difficult to open without pulling on the key, which would have eventually snapped off, so I decided to try these.

They exceeded my expectations. It works just like a handle and you might not ever realize it was a magnet if you didn't know.

I put some on some file drawers that were difficult to grab and they work for that, although, if you try to open the drawer too quickly with them, you might remove the magnet. But these are full 3' wide horizonal file drawers. Pretty impressive.

I use these magnets to hold up a sheet that allows a privacy space for potty. The magnets attach to the car door and frame. They do not slip or let loose even in very breezy conditions.

It was exactly what I was looking for, and very well-made.