When measuring surface roughness, typically the average roughness, Ra, is specified. Ra is a measure of the average of the absolute value of the variation of the surface texture profile about a best-fit mean line. A typical specification for Ra may be 16 microinches, or 0.4 micrometers.
In addition to specifying the long wave cutoff, a short wave cutoff, ls, must be specified. Typically, the ratio of the long wave cutoff to the short wave cutoff is 100:1. Thus an 8-micrometer short wave cutoff may go along with a 0.8-millimeter long wave cutoff to establish a typical measurement bandwidth.
Per ASME B46.1-1995 (p. 36), a standard on surface texture specification, the long wave cutoff length, lc, must be specified on all drawings. Per ISO 1302-2002 (p. 9), a standard on surface texture, the long wave cutoff length, lc, and the short wave cutoff length, ls, must be specified on all drawings.