This part of ISO 75 specifies three methods, using different values of constant flexural stress, which can be used for the determination of the temperature of deflection under load of plastics (including filled plastics and fibre-reinforced plastics in which the fibre length, prior to processing, is up to 7,5 mm) and ebonite: — method A, using a flexural stress of 1,80 MPa; — method B, using a flexural stress of 0,45 MPa; — method C, using a flexural stress of 8,00 MPa.