Socket Mobile Secure Digital Scan Card Series 3 - Manual (Page 36)

36 | APPENDIX B: BAR CODE LABEL SPECIFICATIONS
Tolerance:
The ratio of the widths of bars and spaces in a bar code symbol
must conform to the appropriate AIM bar code specifications and
can cause problems if not correct throughout the bar code.
Problems can occur when bar edges are smeared or rough, or
when they exhibit voids.