ISO 11093-7:2011 specifies a method for the determination, by the three-point method, of the flexural modulus of cylindrical paper and board cores, which meet the following criteria: internal diameter: 50 mm to 350 mm; minimum wall thickness: 0,05 × internal diameter, but not less than 10,0 mm; minimum length of core: 10 × internal diameter, but not less than 1 000 mm.