This International Standard lis s the nominal diameters for the working parts of dental rotating instruments, such as drills, laboratory drills, grinding instruments, diamond instruments, mandrels, etc. and the corresponding designation. It does not apply to diameters for root canal instruments.
ONORM EN 22157-1991 history
1991ONORM EN 22157-1991 Dentistry - Dental rotary instruments -Nominal sizes and designation