Rubber products such as O-rings are prone to dimensional changes after processing and vulcanization, which may be caused by various factors such as die shrinkage or extrusion expansion relaxation. These changes should be determined and considered when designing and manufacturing parts such as moulds and moulds of a product.

GB/T3672.1-2002 "Tolerance of Rubber Products Part I: Dimensional Tolerance" listed in the higher precision tolerance level, only when the final application is required, and should be limited to those considered as key dimensions, the higher the precision used, the more stringent all the control must be implemented in the manufacturing process, because And the higher the cost.

When the product requires some special properties, it is not always possible to provide these properties with a compound that can be molded with precision tolerances. In such cases, the parties concerned shall consult. Generally speaking, vulcanizates with low hardness (i.e. vulcanizates with hardness less than 50 IRHD, see ISO48) require greater tolerance than those with high hardness.

GB/T3672.1-2002 specifies the tolerance level and tolerance value of dimension for compact rubber products by moulding, extrusion and calendering, and also specifies the corresponding test methods required to meet the standard. This standard does not apply to precise annular seals or calendered composite products such as rubber cloth or products coated with rubber by silica gel method.