This standard specifies the basic dimensions of sieve openings of single wire braided mesh, perforated plate and electroformed sheet used as the sieving medium of test sieves. This standard applies to woven wire mesh, perforated sheet and electroformed sheet. In this standard, the basic size of the sieve hole of the wire mesh and the electroformed sheet is less than or equal to 32 μm, and the R'10 series is used as the main size series. In view of the small interval between adjacent basic dimensions smaller than 32 μm, the selection of basic dimensions of the R'10 series is limited. The ratio between adjacent dimensions in the series is shown in Table 1.