This magnet is made of grade N42 neodymium magnet material coated with Ni+Cu+Ni triple layers, which is the best coating technology available. The center hole is 1/8" in diameter with countersunk. If your order contains even number of magnets, half of the countersunk will be on N pole and half of the countersunk will be on S pole. The tolerance of the magnet is industrial standard, i.e. +/-0.0002". This magnet is majorly used for home made wind turbines described in the A Wind Turbine Recipe Book and the DIY package

Magnetic characteristrics of the magnet:
Gauss Rating: 13200 Gauss.
Pulling Force: 72 lbs
Applications: Wind Generators (Hugh Piggott's Plan), Science Projects.
Annotation: There is a hole of 1/8" diameter centered on the flat side of the block


About Neodymium Magnets:
This neodymium magnet is one of rare earth permanent magnet used in Hugh Piggot's Wind Turbine Recipe book. Neodymium magnets are also known as NdFeB magnets, or neo rare earth magnets. Since it's very strong, people also simply call it super strong magnets or super powerful magnets.