What are the usual measurements of neodymium magnets for 3D printing?  

RE: What are the usual measurements of neodymium magnets for 3D printing?

Most commonly used in Prusa projects seems to be N52 20x6x2mm rectangular. They are not easy to find in the US but easier to source in Europe. Next would be 10x2mm round magnets. The popular projects on Printables that require magnets will most likely have been remixed by others to allow for other sizes. 

For neodymium magnets, I always try to get N52 strength.    

RE: What are the usual measurements of neodymium magnets for 3D printing?

Remember that N52 neodymium magnets are strong but have the worst temperature resistance. Above 60 C they can permanently degrade. For anything that might get hot, check the manufacturer's tables. Not sure but there may also be different grades of the same strength. You might have to trade off a small amount of strength for higher temperature resistance. Makes me wonder what type are used in the heat bed!

RE:

Except for the buddy camera magnets (maybe) there is nothing really that should hit 60+. Most of the Printables projects that require magnets are things that stick to the outside of the Core One or are generally out of the way of a heat source. 

Also, latest firmware release seems to force the chamber temperature to cap at 55C. 

The magnetic print bed has been around for a long time now so I assume Prusa thought this through when they added the magnets. 

RE: What are the usual measurements of neodymium magnets for 3D printing?

Another common size is 6x2 mm, which is the standard for the popular Gridfinity system (never understood the appeal of it myself though). I prefer 6x3, which I found easier to source, and holes for 6x3 usually work fine with 6x2 magnets.