Rubber products such as O-rings are prone to dimensional changes after processing and vulcanization, which may be caused by various factors such as molding shrinkage or extrusion expansion relaxation. These changes should be determined and considered when designing and manufacturing components such as molds and mouth shapes for a certain product.

The higher precision tolerance levels listed in GB/T3672.1-2002 "Tolerances for Rubber Products Part 1: Dimensional Tolerances" should only be used when there are requirements for the final application, and should be limited to those dimensions considered critical. The higher the precision used, the stricter the controls that must be implemented during the manufacturing process, resulting in higher costs.

When a product requires certain special properties, using a rubber material that can be molded with precise tolerances may not always provide these properties. In this case, the relevant parties should negotiate. Generally speaking, low hardness vulcanized rubber (i.e. vulcanized rubber with a hardness lower than 50IRHD, see ISO48) requires larger tolerances than high hardness vulcanized rubber.

GB/T3672.1-2002 specifies the dimensional tolerance levels and tolerance values for compact rubber products produced by compression molding, extrusion, and rolling, and also specifies the corresponding test methods required to determine compliance with this standard. This standard does not apply to precision circular sealing rings or rolled composite products such as adhesive tape, or products coated with rubber coatings using silicone methods.