China Neodymium And Ferrite Magnets Manufacturer & Supplier 
For magnets, there are many different descriptions, such as N55, which is described according to the performance level, and some users have asked again, what is the meaning of magnet D55?
Magnet size description of the D55 generally refers to the diameter is 55mm round or ring magnet, D represents the diameter (Diameter), as for the circle or round depends on how many numbers it is, such as 2 data is generally round, such as D55x5mm, that is, the diameter is 55mm, the thickness is 5mm. if it is 3 data, such as D55x20x3mm, that is the outer diameter of the magnet is 55mm, the hole is how much can not be directly determined, because it may be 20mm hole or 3mm hole, different customers describe the magnet, we will generally add the letter d before the hole, such as D55x3mm. Magnet outer diameter is 55mm, the hole is how much can not be directly determined, because it may be 20mm holes, it may be 3mm holes, different customers describe different, we generally add the letter d to the inner hole before, such as D55xd20x3, this marking method is very intuitive.
The following diagram shows the dimensions and magnetization direction of a D55x15mm round magnet.
In addition, D55 magnets can also be drop and impact resistant pot magnets with a steel jacket (steel case) around the magnet for good protection, often used for salvage, where D55 is generally the size that includes the steel case.
As for the material, it can be made of ferrite, neodymium iron boron or samarium cobalt which are commonly used, besides the size, you also need to choose the magnetic grade and surface coating, temperature resistance and so on according to the specific needs, if you don't know which one to choose, you can contact us to provide you with professional advice.
Learn more about magnet terminology: https://www.couragemagnet.com/magnet-terminology/
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