Magnet Shape: Ring with Cylindrical Borehole (Hole)
Material: Sintered Hard Ferrite (Ceramic) and Steel
Coating: nickle       
Grade(Chinese Stardard):         Y35
Magnet ID:              FPCB-70-Y35-Ni  
Detailed magnetic properties data:
Residual Magnetic Flux Density (Br): 4.3-4.5 KGs (mT):  430-450 mT
Intrinsic Coercivity Force (Hcj):    2.70-3.00 KOe    215-239 KA/m
Coercivity Force (Hcb):              2.73-3.03 KOe    217-241 KA/m
Energy Density (BH)max:              4.1-4.8 MGOe     33.1-38.2 KJ/m³
Operating Temperature:               -40 °C to +250 °C
Magnetisation Direction: Axial / Radially magnetized
Pot Magnet Size:
Pot Diameter (D):  70 mm
Pot Height (H):    13 mm
Borehole  (d1):    9 mm
Borehole  (d2):    14 mm
Depth      (t):    7.2 mm
Tolerance:         +/-2% mm
Delivery time           7-25 days
Measurements

Pot magnets with cylindrical borehole
Distinctive feature: These pot magnets can be fastened with a screw without countersink. We also carry pot magnets for counter-sunk screws.
Principle: The strong neodymium magnets are embedded in a steel pot. The steel pot increases the adhesive force of the magnet on direct contact with a thick iron surface. If there is no direct contact with the counterpart, or if the steel plate is thin, painted or rough, you can strain it much less.
Shear force: The indicated adhesive force was measured perpendicular to the surface to which the magnet should stick. It takes a lot less strength to move the magnet sideways. Therefore, you can strain a pot magnet much less if you use it on a wall as opposed to using it on the ceiling.
Rust: These magnets are not rust-proof and therefore intended for dry indoor use.