This part of ISO 4666 establishes general principles for flexometer testing and defines the terms used. Flexometer testing makes possible predictions regarding the durability of rubbers in finished articles subject to dynamic flexing in service such as tyres, bearings, supports, V-belts, and cable-pulley insert rings. However, owing to the wide variations in service conditions, no simple correlation between the accelerated tests specified in the various parts of this International Standard and service performance can be assumed.