1.1 This part of IS0 6916 classifies flexible cellular rubber products known as sponge and expanded rubber. The base material used in their manufacture may be natural rubber, reclaimed rubber or synthetic rubber, either alone or in combination. The only products included in this part of IS0 6916 are in the form of sheeting. 1.2 This part of IS0 6916 does not apply to latex foam rubbers, shoe soling or other similar microcellular products, ebonite cellular rubbers, virgin or reconstituted flexible, semi-rigid urethane foams, virgin or reconstituted poly(vinyl chloride), or poly(vinyl chloride) blended with other polymers. 1.3 Two types are specified, as follows: Type 1: open-cell rubber (normally known as sponge rubber). Type 2: closed-cell rubber (normally known as expanded rubber). These types are further classified by division into classes, based on their relative resistance to the action of petroleum-based oils and/or temperature resistance, and grades, based on a specific range of compression-deflection requirements. The product can be further classified by the addition of a suffix letter to the type, class and grade designation to indicate additional requirements. This letter is then defined by a suffix number denoting a test method. 1.4 Attention is drawn to the fact that most extruded or moulded shapes are of sizes too small for cutting standard test pieces. These are difficult to classify and test by the methods given in this part of IS0 6916 and cannot, therefore, be tested using these procedures. In the case of conflict between the provisions of this part of IS0 6916 and those of the detailed specification or test method for a particular product, the latter shall take precedence. Reference to the methods shall specifically state the desired test or tests.