Magnet Shape: Ring with Cylindrical Borehole (Hole)
Material: Sintered Hard Ferrite (Ceramic) and Steel
Coating: Zinc (Zn)        
Grade(Chinese Stardard):         Y33
Magnet ID:              FPCB-75-Y33-Zn  
Detailed magnetic properties data:
Residual Magnetic Flux Density (Br): 4.1-4.3 KGs (mT):  410-430 mT
Intrinsic Coercivity Force (Hcj):    2.76-3.14 KOe    220-250 KA/m
Coercivity Force (Hcb):              2.83-3.20 KOe    225-255 KA/m
Energy Density (BH)max:              3.9-4.4 MGOe     31.5-35.0 KJ/m³
Operating Temperature:               -40 °C to +250 °C
Magnetisation Direction: Axial / Radially magnetized
Pot Magnet Size:
Pot Diameter (D):  75 mm
Pot Height (H):    13 mm
Borehole  (d1):    9.4 mm
Borehole  (d2):    14.5 mm
Depth      (t):    7 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.