6mm x 6mm N52 

Rare Earth Neodymium Magnet Discs
Specification:
Dimensions: 6mm x 6mm thick 
Tolerances: ±0.1mm x ±0.1mm 
Plating/Coating: Ni-Cu-Ni (Nickel)
Magnetization Direction: Axial (Poles on Flat Ends)
Max Operating Temp: 176ºF (80ºC)
 
Material Features:

N52 grade Magnets are made of a brittle material. These magnets are not as strong as steel.  They are more like a brittle ceramic.  If you let two magnets slam together, they can crack and break.